[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/cx23888-ir.c b/drivers/media/pci/cx23885/cx23888-ir.c
index d51eed0..fa672fe 100644
--- a/drivers/media/pci/cx23885/cx23888-ir.c
+++ b/drivers/media/pci/cx23885/cx23888-ir.c
@@ -1124,7 +1124,7 @@
 }
 
 static int cx23888_ir_s_register(struct v4l2_subdev *sd,
-				 struct v4l2_dbg_register *reg)
+				 const struct v4l2_dbg_register *reg)
 {
 	struct cx23888_ir_state *state = to_state(sd);
 	u32 addr = CX23888_IR_REG_BASE + (u32) reg->reg;