[media] v4l2: make vidioc_s_audout const

Write-only ioctls should have a const argument in the ioctl op.
Do this conversion for vidioc_s_audout.
Adding const for write-only ioctls was decided during the 2012 Media Workshop.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/radio/radio-si4713.c

@@ -83,7 +83,7 @@ static int radio_si4713_g_audout(struct file *file, void *priv,
 }
 
 static int radio_si4713_s_audout(struct file *file, void *priv,
-					struct v4l2_audioout *vao)
+					const struct v4l2_audioout *vao)
 {
 	return vao->index ? -EINVAL : 0;
 }