cxgb4: Add T4 filter support

The T4 architecture is capable of filtering ingress packets at line rate
using the rule in TCAM. If packet hits a rule in the TCAM then it can be either
dropped or passed to the receive queues based on a rule settings.

This patch adds framework for managing filters and to use T4's filter
capabilities. It constructs a Firmware Filter Work Request which writes the
filter at a specified index to get the work done. It hosts shadow copy of
ingress filter entry to check field size limitations and save memory in the
case where the filter table is large.

Signed-off-by: Vipul Pandya <vipul@chelsio.com>
Signed-off-by: Roland Dreier <roland@purestorage.com>