USB: backlight, appledisplay: fix incomplete registration failure handling

On error while registering backlight, return it to caller instead of
returning 0.
Mark struct backlight_ops as const.

Signed-off-by: Bruno Prémont <bonbons@linux-vserver.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 file changed