[media] omap3isp: Don't ignore failure to locate external subdev

A failure to locate the external subdev for a non memory-to-memory
pipeline is a fatal error, don't ignore it.
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Acked-by: Sakari Ailus <sakari.ailus@iki.fi>
Tested-by: Peter Meerwald <pmeerw@pmeerw.net>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>

drivers/media/platform/omap3isp/ispvideo.c

@@ -886,7 +886,7 @@ static int isp_video_check_external_subdevs(struct isp_video *video,
 	struct v4l2_ext_controls ctrls;
 	struct v4l2_ext_control ctrl;
 	unsigned int i;
-	int ret = 0;
+	int ret;
 
 	/* Memory-to-memory pipelines have no external subdev. */
 	if (pipe->input != NULL)
@@ -909,7 +909,7 @@ static int isp_video_check_external_subdevs(struct isp_video *video,
 
 	if (!source) {
 		dev_warn(isp->dev, "can't find source, failing now\n");
-		return ret;
+		return -EINVAL;
 	}
 
 	if (media_entity_type(source) != MEDIA_ENT_T_V4L2_SUBDEV)