mlxsw: spectrum: Use correct netdev when notifying bridge

LAG FDB entries pointing to VLAN devices should be reported to the
bridge with the matching VLAN device and not the underlying LAG device.

Fixes: aac78a44

 ("mlxsw: spectrum: Adjust FDB notifications for VLAN devices")
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>