PowerManager: Don't wake up device when charger is plugged/unplugged (2/2)

This will add the option to disable waking up the device when a charger
is plugged or unplugged.

PS2: hide option if device is already set to never wake up

Change-Id: Iceb685746c4a5a7ea7e393d45d537316db366669
Signed-off-by: Dirk Rettschlag <dirk.rettschlag@gmail.com>