RDMA/hns: Bugfix for checking whether the srq is full when post wr

mainline inclusion
from mainline-v5.12
commit 1620f09b
category: bugfix
bugzilla: NA
CVE: NA

If a user posts WR by wr_list, the head pointer of idx_queue won't be
updated until all wqes are filled, so the judgment of whether head equals
to tail will get a wrong result. Fix above issue and move the head and
tail pointer from the srq structure into the idx_queue structure. After
idx_queue is filled with wqe idx, the head pointer of it will increase.

Signed-off-by: Shunfeng Yang <yangshunfeng2@huawei.com>
Signed-off-by: Yangyang Li <liyangyang20@huawei.com>
Reviewed-by: chunzhi hu <huchunzhi@huawei.com>
Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>