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: Zhenyu Wang <zhenyuw@linux.intel.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
diff --git a/drivers/gpu/drm/i915/intel_bios.c b/drivers/gpu/drm/i915/intel_bios.c
index 1e28c16..4337414 100644
--- a/drivers/gpu/drm/i915/intel_bios.c
+++ b/drivers/gpu/drm/i915/intel_bios.c
@@ -217,6 +217,9 @@
 			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;