input: touchkey: Start/stop touchkey driver based on screen state

* Touchkey driver should only be active when the screen is unblanked.
* This addresses the case where touchkey is active while the screen is
  off due to proximity sensor.

Change-Id: Id84437faa2de1cc81e0f9ebcaab833233774b6e2
i9500: disable Atmel stuff

Change-Id: Ie0bc0851a97e743777a2f6ba8fd85a7526280009