gma500: fix build without backlight device support

gma500: fix build without backlight device support

Fix unmatched curly brackets when CONFIG_BACKLIGHT_CLASS_DEVICE is not
defined.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>