RDMA/hns: Refactor hns_roce_v2_poll_one()

mainline inclusion
from mainline-v5.13-rc1
commit 4940b0ab
category: bugfix
bugzilla: 174002
CVE:NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=4940b0ab458adc9446291a50b61f5e7607f0082b

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Encapsulate the process of obtaining the current QP and filling WC as
functions, also merge some duplicate code.

Link: https://lore.kernel.org/r/1616815294-13434-2-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>