RDMA/hns: Bugfix for CM test

It will print the warning when the MSB bit of SLID is not zero running
cm_req_handler function that test CM. It needs to fixed zero when test
RoCE device.

Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>