cxgb4: add TC-MATCHALL IPv6 support

Matching IPv6 traffic require allocating their own individual slots
in TCAM. So, fetch additional slots to insert IPv6 rules. Also, fetch
the cumulative stats of all the slots occupied by the Matchall rule.

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