RDMA/hns: Use new interfaces to write SRQC

Use new register operation interfaces to simplify the process of write SRQ
Context.

Link: https://lore.kernel.org/r/1611997090-48820-9-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>