net: sched: cls_flower: implement terse dump support

Implement tcf_proto_ops->terse_dump() callback for flower classifier. Only
dump handle, flags and action data in terse mode.

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