csprng - Add copyright & comment around sleep code
drm/i915: Reduce differences with Linux 3.8.13

Mostly in GEM code
drm/i915: Sync intel_ringbuffer.c with Linux 3.8.13

* Preallocate next seqno before touching the ring

* Rearrange code to only have a single method for waiting upon the ring

* Don't allow ring tail to reach the same cacheline as head

* Implement workaround for broken CS tlb on i830/845