RDMA/hns: fix mtr search failure when wqe offset is invalid

driver inclusion
category: bugfix
bugzilla: NA
CVE: NA

Currently, the rq offset is invalid when the rq depth is zero
and sq depth not zero, this will lead the mtr searching fail.

This patch fixes it by adding the invalid wqe offset checking
when an empty mtt is found.

Fixes: 5c42b537063d ("RDMA/hns:Fix bug when wqe num is larger than 16384")

Feature or Bugfix:Bugfix

Signed-off-by: wangxi <wangxi11@huawei.com>
Signed-off-by: Xi Wang <wangxi11@huawei.com>
Reviewed-by: oulijun <oulijun@huawei.com>
Reviewed-by: liuyixian <liuyixian@huawei.com>
Reviewed-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>