drm/i915: Improved w/a for rps on Baytrail

drm/i915: Improved w/a for rps on Baytrail

Rewrite commit 31685c258e0b0ad6aa486c5ec001382cf8a64212
Author: Deepak S <deepak.s@linux.intel.com>
Date:   Thu Jul 3 17:33:01 2014 -0400

    drm/i915/vlv: WA for Turbo and RC6 to work together.

Other than code clarity, the major improvement is to disable the extra
interrupts generated when idle.  However, the reclocking remains rather
slow under the new manual regime, in particular it fails to downclock as
quickly as desired. The second major improvement is that for certain
workloads, like games, we need to combine render+media activity counters
as the work of displaying the frame is split across the engines and both
need to be taken into account when deciding the global GPU frequency as
memory cycles are shared.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Deepak S <deepak.s@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Deepak S<deepak.s@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>