RDMA/hns: Avoid unnecessary memset on WQEs in post_send

All fields of WQE will be rewrote, so the memset is unnecessary. And when
SQ is working in OWNER mode, the pipeline may prefetch the WQEs beyond PI,
the memset operation may flip the owner bit too early, then the pipeline
may get a wrong WQ.

Link: https://lore.kernel.org/r/1612517974-31867-11-git-send-email-liweihang@huawei.com


Signed-off-by: Lang Cheng <chenglang@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>