RDMA/hns: Make the end of sge process more clear

RDMA/hns: Make the end of sge process more clear

Instead of i with the sge number of wr will make the comparision more
clear, that is, when the sge number in wr is small than the maximum
supported sge number in the queue, then a stop sge needed to be filled at
the end of sges in wr.

Link: https://lore.kernel.org/r/1590152579-32364-5-git-send-email-liweihang@huawei.com
Signed-off-by: Yixian Liu <liuyixian@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>