LE releases do not currently overwrite the factory u-boot installed on your device, so if your hardware is wired to support power-on events from the RCU waking the device this will remain working when you install LE. If the hardware does not support RCU wake events no amount of fiddling with u-boot will make it work. If you erased a working factory u-boot for some reason, the easiest solution is restoring the Android ROM/image, then reinstalling LE.
