cxgb4: Add LE hash collision bug fix path in LLD driver

It supports establishing passive open connection through firmware filter work
request. Passive open connection will go through this path as now instead of
listening server we create a server filter which will redirect the incoming SYN
packet to the offload queue.

It divides filter region into regular filters and server filter portion. It
introduces new server filter region which will be exclusively used for creating
server filters. This region will not overlap with regular filter region.

It provides new API cxgb4_alloc_sftid in LLD for getting stid in case of LE
hash collision path. This new stid will be used to open server filter in the
filter region.

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