charger: sync with the current key state on boot

If the power key was down when we booted, we would not have
gotten the down event and thus the device would not have rebooted until
the user released and pressed it again.

Change-Id: Iecb8c3dba773bce4647748715d056e8e1d77f7e0
Signed-off-by: Dima Zavin <dima@android.com>