power: use SCROLL_PREFILING for short interactions

* In the CAF branch, SCROLL_PREFILING is used during interface redrawing, when
  continuous scrolling occurs or possible flinging is expected. Use this hint
  during a short interaction.
* Use SCROLL_VERTICAL if we have scrolling duration information according to CAF.
* For some SoC or devices, the hint variables SCROLL_VERTICAL and SCROLL_PREFILING
  may be different.

Change-Id: I0781f566165c36eb658f755b2e4a10751c730026