RDMA/hns: Simplify process of filling UD SQ WQE

mainline inclusion
from mainline-v5.11-rc1
commit 534c9bdb
category: feature
bugzilla: 174002
CVE:NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=534c9bdb025b68b6c575fbc15976b4470e032691

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There are some codes can be simplified or encapsulated in set_ud_wqe() to
make them easier to be understand.

Link: https://lore.kernel.org/r/1605526408-6936-6-git-send-email-liweihang@huawei.com


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

Reviewed-by: ChunZhi Hu <huchunzhi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>