platform/chrome: cros_ec_lightbar - Add userspace lightbar control bit to EC

Some devices might want to turn off the lightbar if e.g. the
system turns the screen off due to idleness. This prevents the
kernel from going through its normal suspend/resume pathways.

Signed-off-by: Eric Caruso <ejcaruso@chromium.org>
Signed-off-by: Guenter Roeck <groeck@chromium.org>
Signed-off-by: Enric Balletbo i Serra <enric.balletbo@collabora.com>
Signed-off-by: Benson Leung <bleung@chromium.org>