power: Disable the 8974pro-specific display on/off path

 * It's now handled by mpctl directly, and this code does not correctly
   handle the interactive governor. Just disable it as the main
   function does everything we need.

Change-Id: I8fdf9d80bfbf940b55bbe962c1e7a0829bcec14c
Merge branch "cm-11.0" into kylin