power_supply: Add new LED trigger charging-blink-solid-full

Add new trigger to power_supply LEDs. It will blink when battery is
charging, and stay solid when battery is charged. It's usefull to
indicate battery state when there's only one LED available.

Signed-off-by: Vasily Khoruzhick <anarsoul@gmail.com>
Signed-off-by: Anton Vorontsov <cbouatmailru@gmail.com>