PowerManager: Allow to distinguish different keypresses

* Use keypress info to exclude pressing volume keys from
  illuminating HW buttons in config_buttonLightOnKeypressOnly
  mode.

Change-Id: I6bfc7ddd075e12e1ad10c3663a63e80c8d7f983d
Signed-off-by: Corinna Vinschen <xda@vinschen.de>