cxgb4: Check alignment constraint for T6

Update the check for setting  IPV4 filters and align filter_id
to multiple of 2, only for IPv6 filters in case of T6.

Signed-off-by: Arjun Vynipadath <arjun@chelsio.com>
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>