RDMA/hns: Simplify command fields for HEM base address configuration

Use hr_reg_write() instead of roce_set_field() to simplify codes about
configuring HEM BA.

Link: https://lore.kernel.org/r/1616815294-13434-6-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>