net: macvlan: fix memory leaks of macvlan_common_newlink

kmemleak reports memory leaks in macvlan_common_newlink, as follows:

 ip link add link eth0 name .. type macvlan mode source macaddr add
 <MAC-ADDR>

kmemleak reports:

unreferenced object 0xffff8880109bb140 (size 64):
  comm "ip", pid 284, jiffies 4294986150 (age 430.108s)
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 b8 aa 5a 12 80 88 ff ff  ..........Z.....
    80 1b fa 0d 80 88 ff ff 1e ff ac af c7 c1 6b 6b  ..............kk
  backtrace:
    [<ffffffff813e06a7>] kmem_cache_alloc_trace+0x1c7/0x300
    [<ffffffff81b66025>] macvlan_hash_add_source+0x45/0xc0
    [<ffffffff81b66a67>] macvlan_changelink_sources+0xd7/0x170
    [<ffffffff81b6775c>] macvlan_common_newlink+0x38c/0x5a0
    [<ffffffff81b6797e>] macvlan_newlink+0xe/0x20
    [<ffffffff81d97f8f>] __rtnl_newlink+0x7af/0xa50
    [<ffffffff81d98278>] rtnl_newlink+0x48/0x70
    ...

In the scenario where the macvlan mode is configured as 'source',
macvlan_changelink_sources() will be execured to reconfigure list of
remote source mac addresses, at the same time, if register_netdevice()
return an error, the resource generated by macvlan_changelink_sources()
is not cleaned up.

Using this patch, in the case of an error, it will execute
macvlan_flush_sources() to ensure that the resource is cleaned up.

Fixes: aa5fd0fb

 ("driver: macvlan: Destroy new macvlan port if macvlan_common_newlink failed.")
Signed-off-by: Chuang Wang <nashuiliang@gmail.com>
Link: https://lore.kernel.org/r/20221109090735.690500-1-nashuiliang@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>