Input: tm2-touchkey - correct initial brightness

tm2-touchkey doesn't have brightness levels, but only on/off states,
so replace LED_FULL with LED_ON.

Signed-off-by: Jonathan Bakker <xc-racer2@live.ca>
Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>