cxgb4: add ethtool n-tuple filter insertion

Add support to parse and insert ethtool n-tuple filters.
Translate n-tuple spec to flow spec and use the existing tc-flower
offload infra to insert ethtool n-tuple filters.

Signed-off-by: Rahul Lakkireddy <rahul.lakkireddy@chelsio.com>
Signed-off-by: Vishal Kulkarni <vishal@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>