drm/i915/cnl: Extend WM workaround with IPC for CNL

CNL:A & CNL:B have same workaround as KBL to increase wm level latency
by 4us if IPC is enabled.
Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20170817134529.2839-6-mahesh1.kumar@intel.com

drivers/gpu/drm/i915/intel_pm.c

@@ -4492,7 +4492,8 @@ static int skl_compute_plane_wm(const struct drm_i915_private *dev_priv,
 	}
 
 	/* Display WA #1141: kbl,cfl */
-	if ((IS_KABYLAKE(dev_priv) || IS_COFFEELAKE(dev_priv)) &&
+	if ((IS_KABYLAKE(dev_priv) || IS_COFFEELAKE(dev_priv) ||
+	    IS_CNL_REVID(dev_priv, CNL_REVID_A0, CNL_REVID_B0)) &&
 	    dev_priv->ipc_enabled)
 		latency += 4;