[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>

drivers/media/usb/tm6000/tm6000-video.c

@@ -1255,7 +1255,7 @@ static int vidioc_g_frequency(struct file *file, void *priv,
 }
 
 static int vidioc_s_frequency(struct file *file, void *priv,
-				struct v4l2_frequency *f)
+				const struct v4l2_frequency *f)
 {
 	struct tm6000_fh   *fh  = priv;
 	struct tm6000_core *dev = fh->dev;