[media] v4l2: add const to argument of write-only s_frequency ioctl

This ioctl is defined as IOW, so pass the argument as const.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h
index b137a5e..1a82a50 100644
--- a/include/media/v4l2-subdev.h
+++ b/include/media/v4l2-subdev.h
@@ -191,7 +191,7 @@
  */
 struct v4l2_subdev_tuner_ops {
 	int (*s_radio)(struct v4l2_subdev *sd);
-	int (*s_frequency)(struct v4l2_subdev *sd, struct v4l2_frequency *freq);
+	int (*s_frequency)(struct v4l2_subdev *sd, const struct v4l2_frequency *freq);
 	int (*g_frequency)(struct v4l2_subdev *sd, struct v4l2_frequency *freq);
 	int (*g_tuner)(struct v4l2_subdev *sd, struct v4l2_tuner *vt);
 	int (*s_tuner)(struct v4l2_subdev *sd, struct v4l2_tuner *vt);