RDMA/hns: Fix wrong parameters when initial mtt of srq->idx_que

RDMA/hns: Fix wrong parameters when initial mtt of srq->idx_que

The parameters npages used to initial mtt of srq->idx_que shouldn't be
same with srq's. And page_shift should be calculated from idx_buf_pg_sz.
This patch fixes above issues and use field named npage and page_shift
in hns_roce_buf instead of two temporary variables to let us use them
anywhere.

Fixes: 18df508c7970 ("RDMA/hns: Remove if-else judgment statements for creating srq")
Signed-off-by: Weihang Li <liweihang@hisilicon.com>
Link: https://lore.kernel.org/r/1567566885-23088-3-git-send-email-liweihang@hisilicon.com
Signed-off-by: Doug Ledford <dledford@redhat.com>