net: dsa: fix added_by_user switchdev notification

Commit 161d82de ("net: bridge: Notify about !added_by_user FDB
entries") causes the below oops when bringing up a slave interface,
because dsa_port_fdb_add is still scheduled, but with a NULL address.

To fix this, keep the dsa_slave_switchdev_event function agnostic of the
notified info structure and handle the added_by_user flag in the
specific dsa_slave_switchdev_event_work function.

    [   75.512263] Unable to handle kernel NULL pointer dereference at virtual address 00000000
    [   75.519063] pgd = (ptrval)
    [   75.520545] [00000000] *pgd=00000000
    [   75.522839] Internal error: Oops: 17 [#1] ARM
    [   75.525898] Modules linked in:
    [   75.527673] CPU: 0 PID: 9 Comm: kworker/u2:1 Not tainted 4.17.0-rc2 #78
    [   75.532988] Hardware name: Freescale Vybrid VF5xx/VF6xx (Device Tree)
    [   75.538153] Workqueue: dsa_ordered dsa_slave_switchdev_event_work
    [   75.542970] PC is at mv88e6xxx_port_db_load_purge+0x60/0x1b0
    [   75.547341] LR is at mdiobus_read_nested+0x6c/0x78
    [   75.550833] pc : [<804cd5c0>]    lr : [<804bba84>]    psr: 60070013
    [   75.555796] sp : 9f54bd78  ip : 9f54bd87  fp : 9f54bddc
    [   75.559719] r10: 00000000  r9 : 0000000e  r8 : 9f6a6010
    [   75.563643] r7 : 00000000  r6 : 81203048  r5 : 9f6a6010  r4 : 9f6a601c
    [   75.568867] r3 : 00000000  r2 : 00000000  r1 : 0000000d  r0 : 00000000
    [   75.574094] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
    [   75.579933] Control: 10c53c7d  Table: 9de20059  DAC: 00000051
    [   75.584384] Process kworker/u2:1 (pid: 9, stack limit = 0x(ptrval))
    [   75.589349] Stack: (0x9f54bd78 to 0x9f54c000)
    [   75.592406] bd60:                                                       00000000 00000000
    [   75.599295] bd80: 00000391 9f299d10 9f299d68 8014317c 9f7f0000 8120af00 00006dc2 00000000
    [   75.606186] bda0: 8120af00 00000000 9f54bdec 1c9f5d92 8014317c 9f6a601c 9f6a6010 00000000
    [   75.613076] bdc0: 00000000 00000000 9dd1141c 8125a0b4 9f54be0c 9f54bde0 804cd8a8 804cd56c
    [   75.619966] bde0: 0000000e 80143680 00000001 9dce9c1c 81203048 9dce9c10 00000003 00000000
    [   75.626858] be00: 9f54be5c 9f54be10 806abcac 804cd864 9f54be54 80143664 8014317c 80143054
    [   75.633748] be20: ffcaa81d 00000000 812030b0 1c9f5d92 00000000 81203048 9f54beb4 00000003
    [   75.640639] be40: ffffffff 00000000 9dd1141c 8125a0b4 9f54be84 9f54be60 80138e98 806abb18
    [   75.647529] be60: 81203048 9ddc4000 9dce9c54 9f72a300 00000000 00000000 9f54be9c 9f54be88
    [   75.654420] be80: 801390bc 80138e50 00000000 9dce9c54 9f54beac 9f54bea0 806a9524 801390a0
    [   75.661310] bea0: 9f54bedc 9f54beb0 806a9c7c 806a950c 9f54becc 00000000 00000000 00000000
    [   75.668201] bec0: 9f540000 1c9f5d92 805fe604 9ddffc00 9f54befc 9f54bee0 806ab228 806a9c38
    [   75.675092] bee0: 806ab178 9ddffc00 9f4c1900 9f40d200 9f54bf34 9f54bf00 80131e30 806ab184
    [   75.681983] bf00: 9f40d214 9f54a038 9f40d200 9f40d200 9f4c1918 812119a0 9f40d214 9f54a038
    [   75.688873] bf20: 9f40d200 9f4c1900 9f54bf7c 9f54bf38 80132124 80131d1c 9f5f2dd8 00000000
    [   75.695764] bf40: 812119a0 9f54a038 812119a0 81259c5b 9f5f2dd8 9f5f2dc0 9f53dbc0 00000000
    [   75.702655] bf60: 9f4c1900 801320b4 9f5f2dd8 9f4f7e88 9f54bfac 9f54bf80 80137ad0 801320c0
    [   75.709544] bf80: 9f54a000 9f53dbc0 801379a0 00000000 00000000 00000000 00000000 00000000
    [   75.716434] bfa0: 00000000 9f54bfb0 801010e8 801379ac 00000000 00000000 00000000 00000000
    [   75.723324] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
    [   75.730206] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000 00000000 00000000
    [   75.737083] Backtrace:
    [   75.738252] [<804cd560>] (mv88e6xxx_port_db_load_purge) from [<804cd8a8>] (mv88e6xxx_port_fdb_add+0x50/0x68)
    [   75.746795]  r10:8125a0b4 r9:9dd1141c r8:00000000 r7:00000000 r6:00000000 r5:9f6a6010
    [   75.753323]  r4:9f6a601c
    [   75.754570] [<804cd858>] (mv88e6xxx_port_fdb_add) from [<806abcac>] (dsa_switch_event+0x1a0/0x660)
    [   75.762238]  r8:00000000 r7:00000003 r6:9dce9c10 r5:81203048 r4:9dce9c1c
    [   75.767655] [<806abb0c>] (dsa_switch_event) from [<80138e98>] (notifier_call_chain+0x54/0x94)
    [   75.774893]  r10:8125a0b4 r9:9dd1141c r8:00000000 r7:ffffffff r6:00000003 r5:9f54beb4
    [   75.781423]  r4:81203048
    [   75.782672] [<80138e44>] (notifier_call_chain) from [<801390bc>] (raw_notifier_call_chain+0x28/0x30)
    [   75.790514]  r9:00000000 r8:00000000 r7:9f72a300 r6:9dce9c54 r5:9ddc4000 r4:81203048
    [   75.796982] [<80139094>] (raw_notifier_call_chain) from [<806a9524>] (dsa_port_notify+0x24/0x38)
    [   75.804483] [<806a9500>] (dsa_port_notify) from [<806a9c7c>] (dsa_port_fdb_add+0x50/0x6c)
    [   75.811371] [<806a9c2c>] (dsa_port_fdb_add) from [<806ab228>] (dsa_slave_switchdev_event_work+0xb0/0x10c)
    [   75.819635]  r4:9ddffc00
    [   75.820885] [<806ab178>] (dsa_slave_switchdev_event_work) from [<80131e30>] (process_one_work+0x120/0x3a4)
    [   75.829241]  r6:9f40d200 r5:9f4c1900 r4:9ddffc00 r3:806ab178
    [   75.833612] [<80131d10>] (process_one_work) from [<80132124>] (worker_thread+0x70/0x574)
    [   75.840415]  r10:9f4c1900 r9:9f40d200 r8:9f54a038 r7:9f40d214 r6:812119a0 r5:9f4c1918
    [   75.846945]  r4:9f40d200
    [   75.848191] [<801320b4>] (worker_thread) from [<80137ad0>] (kthread+0x130/0x160)
    [   75.854300]  r10:9f4f7e88 r9:9f5f2dd8 r8:801320b4 r7:9f4c1900 r6:00000000 r5:9f53dbc0
    [   75.860830]  r4:9f5f2dc0
    [   75.862076] [<801379a0>] (kthread) from [<801010e8>] (ret_from_fork+0x14/0x2c)
    [   75.867999] Exception stack(0x9f54bfb0 to 0x9f54bff8)
    [   75.871753] bfa0:                                     00000000 00000000 00000000 00000000
    [   75.878640] bfc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000
    [   75.885519] bfe0: 00000000 00000000 00000000 00000000 00000013 00000000
    [   75.890844]  r10:00000000 r9:00000000 r8:00000000 r7:00000000 r6:00000000 r5:801379a0
    [   75.897377]  r4:9f53dbc0 r3:9f54a000
    [   75.899663] Code: e3a02000 e3a03000 e14b26f4 e24bc055 (e5973000)
    [   75.904575] ---[ end trace fbca818a124dbf0d ]---

Fixes: 816a3bed ("switchdev: Add fdb.added_by_user to switchdev notifications")
Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Nikolay Aleksandrov <nikolay@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>