cxgb4: Fix tids count for ipv6 offload connection

the adapter consumes two tids for every ipv6 offload
connection be it active or passive, calculate tid usage
count accordingly.

Also change the signatures of relevant functions to get
the address family.

Signed-off-by: Rizwan Ansari <rizwana@chelsio.com>
Signed-off-by: Varun Prakash <varun@chelsio.com>
Signed-off-by: Ganesh Goudar <ganeshgr@chelsio.com>
Signed-off-by: David S. Miller <davem@davemloft.net>