scsi: pm80xx: Fix dereferencing dangling pointer

sas_task structure should not be used after task_done is called.  If the
device is gone or not attached, we call task_done on t and continue to use
in the sas_task in rest of the function. task_done is pointing to
sas_ata_task_done, may free the memory associated with the task before
returning.

Link: https://lore.kernel.org/r/20191114100910.6153-8-deepak.ukey@microchip.com


Acked-by: Jack Wang <jinpu.wang@cloud.ionos.com>
Signed-off-by: Vikram Auradkar <auradkar@google.com>
Signed-off-by: Deepak Ukey <deepak.ukey@microchip.com>
Signed-off-by: Viswas G <Viswas.G@microchip.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>