exynos3: Implement custom VSYNC IOCTL

* Replace crespo-based VSYNC uevent mechanism in hwcomposer
  with a custom IOCTL mechanism instead (required kernel
  modifications.

* The VSYNC uevents were spamming the Android UEventObserver
  and causing about 7% of constant CPU load

  c86856efabfa0b2981ceb47898dc5873a4998707

Improve custom VSYNC handler in hwcomposer

* only poll when necessary
* solves suspend/resume instability?

  45bf1dae7fa9057a3415151f7559e7bd2a162ead

Change-Id: Icdb5c60059e71688479d390b7b3a1f09a0315a5f