mlxsw: spectrum_router: Do not check VRF MAC address

Commit 74bc9939 ("mlxsw: spectrum_router: Veto unsupported RIF MAC
addresses") enabled the driver to veto router interface (RIF) MAC
addresses that it cannot support.

This check should only be performed for interfaces for which the driver
actually configures a RIF. A VRF upper is not one of them, so ignore it.

Without this patch it is not possible to set an IP address on the VRF
device and use it as a loopback.

Fixes: 74bc9939

 ("mlxsw: spectrum_router: Veto unsupported RIF MAC addresses")
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reported-by: Alexander Petrovskiy <alexpe@mellanox.com>
Tested-by: Alexander Petrovskiy <alexpe@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>