scsi: arcmsr: Ensure getting a free ccb is done under the spin_lock

Ensure getting a free ccb is done under the spin_lock.

Link: https://lore.kernel.org/r/f3ec374cada762149911ff35e92a68a15a7d0327.camel@areca.com.tw
Signed-off-by: ching Huang <ching2048@areca.com.tw>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/arcmsr/arcmsr_hba.c

@@ -3162,10 +3162,12 @@ static int arcmsr_iop_message_xfer(struct AdapterControlBlock *acb,
 
 static struct CommandControlBlock *arcmsr_get_freeccb(struct AdapterControlBlock *acb)
 {
-	struct list_head *head = &acb->ccb_free_list;
+	struct list_head *head;
 	struct CommandControlBlock *ccb = NULL;
 	unsigned long flags;
+
 	spin_lock_irqsave(&acb->ccblist_lock, flags);
+	head = &acb->ccb_free_list;
 	if (!list_empty(head)) {
 		ccb = list_entry(head->next, struct CommandControlBlock, list);
 		list_del_init(&ccb->list);