mlxsw: spectrum: Enable FDB records for VLAN devices on top of LAG

When adding or removing FDB records of VLAN devices on top of LAG we
should set the lag_vid parameter to the VLAN ID of the VLAN device. It
is reserved otherwise.

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>