init: enable pulsing LED on boot

Squash of commits from d2-common:
757670f0 - d2: enable pulsing led while booting
053b652e - d2: prevent boot led from overriding charging led
82a6da8e - d2: prevent boot led from overriding charging led, take 2

Change-Id: I707b1cd51f826808806a2f3852e1b04b4cd5d9ca