RDMA/hns: Refactor the QP context filling process related to WQE buffer configure

Split the code related to WQE buffer configure from the QPC filling
process into two functions: config_qp_sq_buf() and config_qp_rq_buf(),
this will make the code more readable.

Link: https://lore.kernel.org/r/1589982799-28728-9-git-send-email-liweihang@huawei.comSigned-off-by: Xi Wang <wangxi11@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>