scsi: hisi_sas: Add device link between SCSI devices and hisi_hba

Runtime PM of SCSI devices is already supported in SCSI layer, we can
suspend/resume every SCSI device separately. But if there is no link
between hisi_hba and SCSI devices or SCSI targets it will cause issues if
the controller is suspended while SCSI devices are still resuming.  Only
when all the SCSI devices under the controller are suspended, the
controller can be suspended. Add the device link between SCSI devices
and the controller.

Link: https://lore.kernel.org/r/1601649038-25534-6-git-send-email-john.garry@huawei.com
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>