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.

Fixes: c7bcb134 ("RDMA/hns: Add SRQ support for hip08 kernel mode")
Link: https://lore.kernel.org/r/1611997090-48820-3-git-send-email-liweihang@huawei.comSigned-off-by: NWenpeng Liang <liangwenpeng@huawei.com>
Signed-off-by: NWeihang Li <liweihang@huawei.com>
Signed-off-by: NJason Gunthorpe <jgg@nvidia.com>