Atm, only the button wake up reason was trigerring postwake. This make
the usb charger to uncrust the phone and leave it in lock or off mode.
Now postwake take an argument which is the wake up reason.
The modem reason should not manage so phone state so we make it explicit
in the default hook.
"usb power" and "button" now make the phone to blink 5 seconds and put
the phone back to crust.
