virt: fsl_hypervisor: Directly return 0 instead of using local ret variable

fixes coccinelle warning:
drivers/virt/fsl_hypervisor.c:690:5-8: Unneeded variable: "ret". Return "0" on line 698
Signed-off-by: Haowen Bai <baihaowen@meizu.com>
Link: https://lore.kernel.org/r/1646966331-16813-1-git-send-email-baihaowen@meizu.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/virt/fsl_hypervisor.c

@@ -687,15 +687,13 @@ static int fsl_hv_close(struct inode *inode, struct file *filp)
 	struct doorbell_queue *dbq = filp->private_data;
 	unsigned long flags;
 
-	int ret = 0;
-
 	spin_lock_irqsave(&db_list_lock, flags);
 	list_del(&dbq->list);
 	spin_unlock_irqrestore(&db_list_lock, flags);
 
 	kfree(dbq);
 
-	return ret;
+	return 0;
 }
 
 static const struct file_operations fsl_hv_fops = {