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/platform/x86/eeepc-laptop.c b/drivers/platform/x86/eeepc-laptop.c
index b2edfdc..c062a65 100644
--- a/drivers/platform/x86/eeepc-laptop.c
+++ b/drivers/platform/x86/eeepc-laptop.c
@@ -1115,7 +1115,7 @@
 	return set_brightness(bd, bd->props.brightness);
 }
 
-static struct backlight_ops eeepcbl_ops = {
+static const struct backlight_ops eeepcbl_ops = {
 	.get_brightness = read_brightness,
 	.update_status = update_bl_status,
 };