[Intel-gfx] i915_wait_request scaling

[Chris Wilson]

The first 3 patches are cc:stable for reducing the negative
side-effects of busywaiting. Following on from them, we have a set of
patches to prevent the thundering herd issue with multiple concurrent
waiters and to optimise the waiters. Since this has been flagged as
severely impacting some client loads, I've moved this forward of the
series to cut the execbuffer overheads.

Available as:
http://cgit.freedesktop.org/~ickle/linux-2.6/log/?h=breadcrumbs
-Chris