cxgb4: Correct ntuple mask validation for hash filters

Earlier code of doing bitwise AND with field width bits was wrong.
Instead, simplify code to calculate ntuple_mask based on supplied
fields and then compare with mask configured in hw - which is the
correct and simpler way to validate ntuple mask.

Fixes: 3eb8b62d ("cxgb4: add support to create hash-filters via tc-flower offload")
Signed-off-by: Kumar Sanghvi <kumaras@chelsio.com>
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>