drm/i915/tgl: PSR link standby is not supported anymore

According to BSpc if link standby is set on TGL+, PSR will not be
enabled. Vendors should not use panels that requires link standby and
even if they do, panel should assert a PSR error that will cause PSR to
be disabled.

BSpec: 50434
Signed-off-by: José Roberto de Souza <jose.souza@intel.com>
Signed-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Reviewed-by: Anshuman Gupta <anshuman.gupta@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190823082055.5992-8-lucas.demarchi@intel.com

drivers/gpu/drm/i915/display/intel_psr.c

@@ -1283,8 +1283,8 @@ void intel_psr_init(struct drm_i915_private *dev_priv)
 	if (IS_HASWELL(dev_priv) || IS_BROADWELL(dev_priv))
 		/* HSW and BDW require workarounds that we don't implement. */
 		dev_priv->psr.link_standby = false;
-	else
-		/* For new platforms let's respect VBT back again */
+	else if (INTEL_GEN(dev_priv) < 12)
+		/* For new platforms up to TGL let's respect VBT back again */
 		dev_priv->psr.link_standby = dev_priv->vbt.psr.full_link;
 
 	INIT_WORK(&dev_priv->psr.work, intel_psr_work);