RDMA/hns: Bugfix for atomic operation

The atomic operation not supported inline. Besides, the standard atomic
operation only support a sge and the sge is placed in the wqe.

Fix: 384f8818("RDMA/hns: Add atomic support")
Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>