Input: qt2160 - add support for LEDs

Outputs x8..x0 of the qt2160 can have leds attached to it.
This patch handles those outputs using the generic LED
framework.

The PWM controls available in the chip are used to achieve
different levels of brightness.

Signed-off-by: Javier Martin <javier.martin@vista-silicon.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>