mlxsw: spectrum: Apply RIF configuration when joining a LAG

In case a router interface (RIF) is configured for a LAG, make sure its
configuration is applied on the new LAG member.

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