cxgb4: Differentiate between stids between server and filter region

For T4 adapter, offloaded servers tid for IPv4 connections are
allocated from filter region. So add a new field for server filter tid if
server tid is allocated from filter region.

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