RDMA/hns: Refactor the MTR creation flow

mainline inclusion
from mainline-v5.12-rc1
commit 0e0ab04b
category: bugfix
bugzilla: 174002
CVE:NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=0e0ab04b5bbe84b58097d6dabb3b01b93ce2bf77

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

Split the hns_roce_mtr_create() into serval small functions, remove unused
member in 'struct hns_roce_buf_attr' and delete unnecessary MTR page count
check flow to make the MTR creation related codes clearer.

Link: https://lore.kernel.org/r/1611395282-991-2-git-send-email-liweihang@huawei.com


Signed-off-by: Xi Wang <wangxi11@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>