The 'HNS_ROCE_OPC_QUERY_MB_ST' command will response the mailbox complete
status and hardware busy flag, and the complete status is only valid when
the busy flag is 0, so it's better to query these two fields at a time
rather than separately.

Link: https://lore.kernel.org/r/1616815294-13434-4-git-send-email-liweihang@huawei.comSigned-off-by: NXi Wang <wangxi11@huawei.com>
Signed-off-by: NWeihang Li <liweihang@huawei.com>
Signed-off-by: NJason Gunthorpe <jgg@nvidia.com>