Revert "drm/i915/vlv: Remove check for Old Ack during forcewake"

Revert "drm/i915/vlv: Remove check for Old Ack during forcewake"

This reverts commit 9906f3b0855d210136ff6995c603a35b1a70c508.

While the relevance for WaRsDontPollForAckOnClearingFWBits is under
investigation, revert this as regression.

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=85684
Tested-by:   Tested-by: lu hua <huax.lu@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: S, Deepak <deepak.s@intel.com>
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>