drm/i915/chv: Implement WaDisableSamplerPowerBypass for CHV

Cherryview also needs this WA.

Signed-off-by: Rafael Barbalho <rafael.barbalho@intel.com>
[vsyrjala: Looks like it's for pre-prodution hw only]
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>