[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/usb/gspca/pac7302.c b/drivers/media/usb/gspca/pac7302.c
index 682ef33..6008c8d 100644
--- a/drivers/media/usb/gspca/pac7302.c
+++ b/drivers/media/usb/gspca/pac7302.c
@@ -840,7 +840,7 @@
 
 #ifdef CONFIG_VIDEO_ADV_DEBUG
 static int sd_dbg_s_register(struct gspca_dev *gspca_dev,
-			struct v4l2_dbg_register *reg)
+			const struct v4l2_dbg_register *reg)
 {
 	u8 index;
 	u8 value;