scsi: hisi_sas: Factor out task prep and delivery code

The task prep code is the same between the normal path (in
hisi_sas_task_prep()) and the internal abort path, so factor is out into a
common function.

Link: https://lore.kernel.org/r/1639579061-179473-5-git-send-email-john.garry@huawei.comSigned-off-by: John Garry <john.garry@huawei.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>