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

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

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Acked-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Acked-by: Lad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/pci/cx23885/cx23885-ioctl.h b/drivers/media/pci/cx23885/cx23885-ioctl.h
index 315be0c..a608096 100644
--- a/drivers/media/pci/cx23885/cx23885-ioctl.h
+++ b/drivers/media/pci/cx23885/cx23885-ioctl.h
@@ -33,7 +33,7 @@
 
 
 int cx23885_s_register(struct file *file, void *fh,
-		       struct v4l2_dbg_register *reg);
+		       const struct v4l2_dbg_register *reg);
 
 #endif
 #endif