net/sched: cls_flower: Add support for matching on flags

Add UAPI to provide set of flags for matching, where the flags
provided from user-space are mapped to flow-dissector flags.

The 1st flag allows to match on whether the packet is an
IP fragment and corresponds to the FLOW_DIS_IS_FRAGMENT flag.

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