Revert drm i915 Workaround of LLC incoherence

Revert drm i915 Workaround incoherence between fences and LLC across multiple CPUs
The workaround was obsoleted by a faster, better fix that uses 32 bit write instead of 64-bit writes.
Merge pull request #3 from LunarG/revert_25ff119

Revert drm i915 Workaround of LLC incoherence