leds-bcm6328: simplify and improve default-state handling

This patch simplifies and improves the code related to
default-state handling.
It also changes the code to power off the LEDs by default.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>