backlight: constify backlight_ops

backlight_device_register has been expecting a const "ops" argument, and using
it as such, since 9905a43b2d563e6f89e4c63c4278ada03f2ebb14. Let's make the
remaining backlight_ops instances const.

Inspired by hunks of the grsecurity patch, updated for newer kernels.

Signed-off-by: Lionel Debroux <lionel_debroux@yahoo.fr>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
diff --git a/drivers/video/omap2/displays/panel-taal.c b/drivers/video/omap2/displays/panel-taal.c
index e1c765d..61026f9 100644
--- a/drivers/video/omap2/displays/panel-taal.c
+++ b/drivers/video/omap2/displays/panel-taal.c
@@ -465,7 +465,7 @@
 	return 0;
 }
 
-static struct backlight_ops taal_bl_ops = {
+static const struct backlight_ops taal_bl_ops = {
 	.get_brightness = taal_bl_get_intensity,
 	.update_status  = taal_bl_update_status,
 };