drm/i915: Remove CNL from WA 827

CNL A stepping was the only affected there.
But also it is time to clean old pre-production
CNL Workarounds, so let's just remove and clean
this W/A.

Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Clint Taylor <Clinton.A.Taylor@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181031162845.12419-4-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/intel_display.c

@@ -5224,8 +5224,8 @@ static bool needs_nv12_wa(struct drm_i915_private *dev_priv,
 	if (!crtc_state->nv12_planes)
 		return false;
 
-	if ((IS_GEN9(dev_priv) && !IS_GEMINILAKE(dev_priv)) ||
-	    IS_CANNONLAKE(dev_priv))
+	/* WA Display #0827: Gen9:all */
+	if (IS_GEN9(dev_priv) && !IS_GEMINILAKE(dev_priv))
 		return true;
 
 	return false;