[Intel-gfx] drm/i915/hsw/bdw: Enable resource streamer v3

[Abdiel Janulgue]

Hi,

Although most of this patches were alread reviewed, I am resending them
due to additional changes suggested by Jani Nikula. In addition
Mesa folks want RS to be working with hiccups on GEN8 as well so
I added the necessary support for that platform as well.

Changes since last posting:
- Make RS context save and restore work properly on GEN8
- Add I915_PARAM_HAS_RESOURCE_STREAMER params.

[PATCH 1/3] drm/i915: Enable resource streamer bits on
[PATCH 2/3] drm/i915: Enable Resource Streamer state save/restore
[PATCH 3/3] drm/i915: Expose I915_EXEC_RESOURCE_STREAMER flag