The /usr/bin/power_key.py script basically does 2 things:

* set a devfreq governor once (and handle frequencies but only on old kernels)
* shut down the system when the power button is being pressed for ca. 2 seconds

The first task is to be replaced via a simple udev rule. The second one
is being tracked by OS-issues#146


and will be replaced by a GUI anyways.

This solves problems with the power_key script:
* it is not syncronised with the display system.
* it is a nightmare to maintain and keep working

In my tests, the long-press shutdown mechanism didn't work anymore, but if
it does for you, this will remove it (temporarily, see the above issue).

Signed-off-by: Martin Kepplinger <martin.kepplinger@puri.sm>