RDMA/hns: optimize mtr management and fix mtr addressing bug

driver inclusion
category: Bugfix
bugzilla: NA

This modification is mainly to optimize mtr management
 and solve mtr addressing bug:When mtt_ba_pg_sz = 0,
hem-> start / step = 1, which eventually results in an
 additional BA_BYTE_LEN added to the offset

Signed-off-by: Tao Jihua <taojihua4@huawei.com>
Reviewed-by: Hu Chunzhi <huchunzhi@huawei.com>
Reviewed-by: Wang Lin <wanglin137@huawei.com>
Reviewed-by: Zhao Weibo <zhaoweibo3@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>