mlxsw: spectrum: Remove unnecessary check in FDB processing

We now offload the learning configuration to the device and don't rely
on the driver to decide whether to learn the FDB record, so remove the
check.

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>