scsi: aic79xx: Fix up NULL command in ahd_done()

Found by smatch.

Fixes: c67e6380 ("scsi: aic79xx: Do not reference SCSI command when resetting device")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Link: https://lore.kernel.org/r/20231023073014.21438-1-hare@suse.de


Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>