mlxsw: spectrum: Adjust switchdev ops for VLAN devices

switchdev ops can now be called for VLAN devices and we need to be
prepared for it. Until now they were only called for the port netdev.

Use the newly propagated orig_dev passed as part of the switchdev
attr/obj and determine whether the original device is a VLAN device. If
so, act accordingly, otherwise continue as usual.

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