[media] soc_camera: preserve const attribute

drivers/media/video/soc_camera.c: In function ‘soc_camera_video_start’:
drivers/media/video/soc_camera.c:1515: warning: initialization discards qualifiers from pointer target type
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/soc_camera.c

@@ -1512,7 +1512,7 @@ static int video_dev_create(struct soc_camera_device *icd)
  */
 static int soc_camera_video_start(struct soc_camera_device *icd)
 {
-	struct device_type *type = icd->vdev->dev.type;
+	const struct device_type *type = icd->vdev->dev.type;
 	int ret;
 
 	if (!icd->dev.parent)