cxgb4: add common api support for configuring filters

Enable filters for non-offload configuration and add common api support
for setting and deleting filters in LE-TCAM region of the hardware.

IPv4 filters occupy one slot.  IPv6 filters occupy 4 slots and must
be on a 4-slot boundary.  IPv4 filters can not occupy a slot belonging
to IPv6 and the vice-versa is also true.

Filters are set and deleted asynchronously.  Use completion to wait
for reply from firmware in order to allow for synchronization if needed.

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