drm/i915: Fix SSC frequence for IGDNG

IGDNG LVDS SSC uses 120Mhz freq. This fixes one
1600x900 LVDS panel black issue on IGDNG with SSC enabled.

Cc: Stable Team <stable@kernel.org>
Signed-off-by: NZhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: NJesse Barnes <jbarnes@virtuousgeek.org>

drivers/gpu/drm/i915/intel_bios.c

@@ -217,6 +217,9 @@ parse_general_features(struct drm_i915_private *dev_priv,
 			if (IS_I85X(dev_priv->dev))
 				dev_priv->lvds_ssc_freq =
 					general->ssc_freq ? 66 : 48;
+			else if (IS_IGDNG(dev_priv->dev))
+				dev_priv->lvds_ssc_freq =
+					general->ssc_freq ? 100 : 120;
 			else
 				dev_priv->lvds_ssc_freq =
 					general->ssc_freq ? 100 : 96;