scsi: pm8001: Use sas_task_find_rq() for tagging

scsi: pm8001: Use sas_task_find_rq() for tagging

The request associated with a SCSI command coming from the block layer has
a unique tag, so use that when possible for getting a CCB.

Unfortunately we don't support reserved commands in the SCSI midlayer yet,
so in the interim continue to manage those tags internally (along with
tags for private commands).

Signed-off-by: John Garry <john.garry@huawei.com>
Link: https://lore.kernel.org/r/1666091763-11023-6-git-send-email-john.garry@huawei.com
Reviewed-by: Jack Wang <jinpu.wang@ionos.com>
Reviewed-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>