lantiq: add support for indicating the boot state using three leds

lantiq: add support for indicating the boot state using three leds

The BTHOMEHUBV5A has a RGB power led, where every colour is perfect to
indicate the current boot state. This patch adds support for such cases.

The existing led sequences should be the same as before.

Boards which are using a led different from power (like TDW89x0) are
changed to switch of the led after boot

Signed-off-by: Mathias Kresin <openwrt@kresin.me>
SVN-Revision: 48041