[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/include/media/v4l2-ioctl.h b/include/media/v4l2-ioctl.h
index ee7b7c6..a4175cd 100644
--- a/include/media/v4l2-ioctl.h
+++ b/include/media/v4l2-ioctl.h
@@ -242,7 +242,7 @@
 	int (*vidioc_g_register)       (struct file *file, void *fh,
 					struct v4l2_dbg_register *reg);
 	int (*vidioc_s_register)       (struct file *file, void *fh,
-					struct v4l2_dbg_register *reg);
+					const struct v4l2_dbg_register *reg);
 #endif
 	int (*vidioc_g_chip_ident)     (struct file *file, void *fh,
 					struct v4l2_dbg_chip_ident *chip);