[media] media: sh_vou: fix const cropping related warnings

A recent commit "[media] v4l2: make vidioc_s_crop const" introduced
warnings in sh_vou. Fix them by cleanly separating writable and
read-only variables in cropping operations.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/platform/sh_vou.c

@@ -935,9 +935,10 @@ static int sh_vou_g_crop(struct file *file, void *fh, struct v4l2_crop *a)
 /* Assume a dull encoder, do all the work ourselves. */
 static int sh_vou_s_crop(struct file *file, void *fh, const struct v4l2_crop *a)
 {
+	struct v4l2_crop a_writable = *a;
 	struct video_device *vdev = video_devdata(file);
 	struct sh_vou_device *vou_dev = video_get_drvdata(vdev);
-	struct v4l2_rect *rect = &a->c;
+	struct v4l2_rect *rect = &a_writable.c;
 	struct v4l2_crop sd_crop = {.type = V4L2_BUF_TYPE_VIDEO_OUTPUT};
 	struct v4l2_pix_format *pix = &vou_dev->pix;
 	struct sh_vou_geometry geo;