[Intel-gfx] Premature unpinning, finally?

[Chris Wilson]

Now we have the context leak sorted, everything should be in place to
satisfy BAT, or so I hope. A few new patches need reviewing, and the rest
could do with eyeballing - though I have tried to keep them the same, the
code around them has changed slightly, and I hope I have introduced subtle
bugs in the rebasing. 

[PATCH v6 12/25] drm/i915: Unify intel_ring_begin()
[PATCH v6 13/25] drm/i915: Remove the identical implementations of
[PATCH v6 14/25] drm/i915: Manually unwind after a failed request
[PATCH v6 15/25] drm/i915: Preallocate enough space for the average
[PATCH v6 16/25] drm/i915: Update execlists context descriptor format

are new.
-Chris