mlxsw: spectrum: Adjust FDB notifications for VLAN devices

FDB notifications contain the FID and port (or LAG ID) on which the MAC
was learned. In the case of the 802.1Q bridge one can easily derive the
matching VID - as FID equals VID - and generate the appropriate
notification for the software bridge. With VLAN devices this is no
longer the case, as these are associated with a vFID.

Solve that by converting the FID to a vFID and lookup the matching VLAN
device. From that derive the VID and whether learning (and learning
sync) should occur.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>