drm/i915: Drop WaIncreaseLatencyIPCEnabled/1140 for cnl

Drop WaIncreaseLatencyIPCEnabled/Display w/a #1140 for
early cnl steppings.

v2: Drop the IS_GEN9_BC() change since other related
    parts of the code also use the KBL||CFL pattern

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190503173807.10834-2-ville.syrjala@linux.intel.com

drivers/gpu/drm/i915/intel_pm.c

@@ -4786,8 +4786,7 @@ static void skl_compute_plane_wm(const struct intel_crtc_state *cstate,
 	 * WaIncreaseLatencyIPCEnabled: kbl,cfl
 	 * Display WA #1141: kbl,cfl
 	 */
-	if ((IS_KABYLAKE(dev_priv) || IS_COFFEELAKE(dev_priv) ||
-	    IS_CNL_REVID(dev_priv, CNL_REVID_A0, CNL_REVID_B0)) &&
+	if ((IS_KABYLAKE(dev_priv) || IS_COFFEELAKE(dev_priv)) ||
 	    dev_priv->ipc_enabled)
 		latency += 4;