net/sched: cls_flower: Specify vlan attributes format in the UAPI header

Specify the format (size and endianess) for the vlan attributes.

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