RDMA/hns: Fix configuration of ack_req_freq in QPC

The hardware will add AckReq flag in BTH header according to the value of
ack_req_freq to request ACK from responder for the packets with this flag.
It should be greater than or equal to lp_pktn_ini instead of using a fixed
value.

Fixes: 7b9bd73e

 ("RDMA/hns: Fix wrong assignment of lp_pktn_ini in QPC")
Link: https://lore.kernel.org/r/1600509802-44382-8-git-send-email-liweihang@huawei.com
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>