mlxsw: spectrum_switchdev: Remove VXLAN checks during FID membership

As explained in previous patch, VXLAN devices now take a reference on
the FID and not only local ports. Therefore, there is no need for local
ports to check if they need to set a VNI on the FID when they join the
FID.

Remove these unnecessary checks.

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