All RIF types are associated with a virtual router (VR), so determine VR
first when creating a RIF.

That way, we can more easily integrate the common RIF core in the
following patches.
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>