drm fixes for 4.8-rc6

i915, vc4 and atmel.
Merge tag 'drm-vc4-fixes-2016-09-14' of https://github.com/anholt/linux into drm-fixes

This pull request brings in a fix for crashes in X on VC4.

* tag 'drm-vc4-fixes-2016-09-14' of https://github.com/anholt/linux:
  drm/vc4: mark vc4_bo_cache_purge() static
  drm/vc4: Allow some more signals to be packed with uniform resets.