bnx2x: allow adding VLANs while interface is down

Since implementing VLAN filtering in commit 05cc5a39


("bnx2x: add vlan filtering offload") bnx2x refuses to add a VLAN while
the interface is down:

  # ip link add link enp3s0f0 enp3s0f0_10 type vlan id 10
  RTNETLINK answers: Bad address

and in dmesg (with bnx2x.debug=0x20):
  bnx2x: [bnx2x_vlan_rx_add_vid:12941(enp3s0f0)]Ignoring VLAN
  configuration the interface is down

Other drivers have no problem with this.
Fix this peculiar behavior in the following way:
 - Accept requests to add/kill VID regardless of the device state.
   Maintain the requested list of VIDs in the bp->vlan_reg list.
 - If the device is up, try to configure the VID list into the hardware.
   If we run out of VLAN credits or encounter a failure configuring an
   entry, fall back to accepting all VLANs.
   If we successfully configure all entries from the list, turn the
   fallback off.
 - Use the same code for reconfiguring VLANs during NIC load.

Signed-off-by: Michal Schmidt <mschmidt@redhat.com>
Acked-by: Yuval Mintz <Yuval.Mintz@qlogic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>