The corruption in CSB mmio reads we were seeing has been tracked down to
incorrectly touching forcewake of all domains, following an engine reset.
It is still a mistery why we only catched this in Broxton, since it
could happen in any platform.

With that fix already merged, commit 4055dc75 ("drm/i915: Stop
touching forcewake following a gen6+ engine reset"), lets try to enable
per-engine resets in Broxton one more time.

This reverts commit f188258bde0f ("drm/i915: Disable per-engine reset for
Broxton").

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Michel Thierry <michel.thierry@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170818172342.7282-1-michel.thierry@intel.comTested-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>