RDMA/hns: Bugfix for posting a wqe with sge

RDMA/hns: Bugfix for posting a wqe with sge

Driver should first check whether the sge is valid, then fill the valid
sge and the caculated total into hardware, otherwise invalid sges will
cause an error.

Fixes: 52e3b42a2f58 ("RDMA/hns: Filter for zero length of sge in hip08 kernel mode")
Fixes: 7bdee4158b37 ("RDMA/hns: Fill sq wqe context of ud type in hip08")
Link: https://lore.kernel.org/r/1578571852-13704-1-git-send-email-liweihang@huawei.com
Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>