RDMA/hns: Refactor hns_roce_create_srq()

mainline inclusion
from mainline-v5.12-rc1
commit 0fee4516
category: bugfix
bugzilla: 174002
CVE:NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0fee451634969cd132a0101824ef2558b2b389be

----------------------------------------------------------------------

Split the SRQ creation process into multiple steps and encapsulate them
into functions.

Link: https://lore.kernel.org/r/1611997090-48820-7-git-send-email-liweihang@huawei.com


Signed-off-by: Wenpeng Liang <liangwenpeng@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>