RDMA/hns: Add memory barrier when writing hw

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

It is the right way to add memory barrier when writing hw.

Feature or Bugfix:Bugfix

Signed-off-by: liyangyang (M) <liyangyang20@huawei.com>
Reviewed-by: oulijun <oulijun@huawei.com>
Reviewed-by: liuyixian <liuyixian@huawei.com>
Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>