scsi: hisi_sas: initialize dq spinlock before use

It is required to initialize the dq spinlock before use, which was not being
done, so fix it. This issue can be detected when CONFIG_DEBUG_SPINLOCK is
enabled.

Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>