scsi: hisi_sas: check for SAS_TASK_STATE_ABORTED in slot complete

Check in slot_complete_v2_hw() for whether a task has already been
completed by upper layer.

Signed-off-by: John Garry <john.garry@huawei.com>
Reviewed-by: Xiang Chen <chenxiang66@hisilicon.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>