scsi: aacraid: Introduce aac_scsi_done()

This patch does not change any functionality but makes the next patch in
this series easier to read.

Link: https://lore.kernel.org/r/20211007202923.2174984-16-bvanassche@acm.org


Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>