cxgb4: add support to create hash-filters via tc-flower offload

Determine whether the flow classifies as exact-match with respect to
4-tuple and configured tuple mask in hw. If successfully classified
as exact-match, offload the flow as hash-filter in hw.

Signed-off-by: Kumar Sanghvi <kumaras@chelsio.com>
Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>