selftests: mlxsw: Test FID RIF MAC vetoing

When a FID RIF is created for a bridge with IP address, its MAC address
must obey the same requirements as other RIFs. Test that attempts to
change the address incompatibly by attaching a device are vetoed with
extack.

Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>