cxgb4: introduce fw_filter2_wr to prepare for L3/L4 rewrite support

Update driver to use new fw_filter2_wr in order to support rewrite of
L3/L4 header fields via filters. Query FW_PARAMS_PARAM_DEV_FILTER2_WR
to check whether FW supports this new wr.

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>