Fading Notification LED

Slowly pulse led (by xplodwild)
Make led fade switchable (echo "0">led_fade to disable fading, 1 to enable) (by xplodwild)
No hacksung :( (by xplodwild)
an30259: support reading of led_fade sysfs (by codeworkx)
an30259a: don't restrict led brightness in user case (by codeworkx)

Change-Id: I665a178771708f64ce1d23455dab91cf72e38b4d

Modified sysfs interface, store only accepts 0 or 1 (disable or enable), show will be more helpful