scsi: hisi_sas: Check before using pointer variables

In commit 4b329ab ("scsi: hisi_sas: Move slot variable definition in
hisi_sas_abort_task()"), we move the variables slot to the function head.
However, the variable slot may be NULL, we should check it in each branch.

Fixes: 4b329ab ("scsi: hisi_sas: Move slot variable definition in hisi_sas_abort_task()")
Signed-off-by: Yihang Li <liyihang9@huawei.com>
Signed-off-by: Xiang Chen <chenxiang66@hisilicon.com>
Link: https://lore.kernel.org/r/1702525516-51258-4-git-send-email-chenxiang66@hisilicon.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

Author: Yihang Li

drivers/scsi/hisi_sas/hisi_sas_main.c

@@ -1641,7 +1641,10 @@ static int hisi_sas_abort_task(struct sas_task *task)
 	task->task_state_flags |= SAS_TASK_STATE_ABORTED;
 	spin_unlock_irqrestore(&task->task_state_lock, flags);
 
-	if (slot && task->task_proto & SAS_PROTOCOL_SSP) {
+	if (!slot)
+		goto out;
+
+	if (task->task_proto & SAS_PROTOCOL_SSP) {
 		u16 tag = slot->idx;
 		int rc2;
 
@@ -1688,7 +1691,7 @@ static int hisi_sas_abort_task(struct sas_task *task)
 				rc = hisi_sas_softreset_ata_disk(device);
 			}
 		}
-	} else if (slot && task->task_proto & SAS_PROTOCOL_SMP) {
+	} else if (task->task_proto & SAS_PROTOCOL_SMP) {
 		/* SMP */
 		u32 tag = slot->idx;
 		struct hisi_sas_cq *cq = &hisi_hba->cq[slot->dlvry_queue];