This will allow FW to not send more data to TP (which would then need to
be buffered). Pass the negotiated TCP window scale to FW in the FLOWC WR.

Also refactor send_flowc() a bit to clean it up.
Signed-off-by: NSteve Wise <swise@opengridcomputing.com>
Signed-off-by: NPotnuri Bharat Teja <bharat@chelsio.com>
Signed-off-by: NJason Gunthorpe <jgg@mellanox.com>