media: ti: davinci: vpbe_display.c: return 0 instead of 'ret'.

Since 'ret' is known to be 0, just return '0'. This fixes a smatch warning:

vpbe_display.c:1152 vpbe_display_open() warn: missing error code? 'err'
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Cc: "Lad, Prabhakar" <prabhakar.csengg@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>

drivers/media/platform/ti/davinci/vpbe_display.c

@@ -1149,7 +1149,7 @@ static int vpbe_display_open(struct file *file)
 
 	/* leaving if layer is already initialized */
 	if (!v4l2_fh_is_singular_file(file))
-		return err;
+		return 0;
 
 	if (!layer->usrs) {
 		if (mutex_lock_interruptible(&layer->opslock))