RDMA/hns: Use the core code to manage the fixed mmap entries

mainline inclusion
from mainline-v5.15-rc1
commit 6d202d9f
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/I4O23M
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git/commit/?id=6d202d9f70a33560ab62b81da2b062c936437e54

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Add a new implementation for mmap by using the new mmap entry API. This
makes way for further use of the dynamic mmap allocator in this driver.

Link: https://lore.kernel.org/r/20211028105640.1056-1-liangwenpeng@huawei.com


Signed-off-by: Chengchang Tang <tangchengchang@huawei.com>
Signed-off-by: Yixing Liu <liuyixing1@huawei.com>
Signed-off-by: Wenpeng Liang <liangwenpeng@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
sigend-off-by: Guofeng Yue <yueguofeng@hisilicon.com>

Reviewed-by: Yangyang Li <liyangyang20@huawei.com>
Acked-by: Xie XiuQi <xiexiuqi@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>