mlxsw: Pass switch ID through devlink_port_attrs_set()

Pass the switch ID down the to devlink through devlink_port_attrs_set()
so it can be used by devlink_compat_switch_id_get().

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