drm/i915: Make sure we don't detect eDP on g4x

We don't support eDP on g4x, so let's not even look at the VBT
to determine the port type, just in case the VBT is bonkers
on some g4x machines and indicates the precense of eDP.
Signed-off-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: NJani Nikula <jani.nikula@intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/intel_dp.c

@@ -5255,6 +5255,13 @@ bool intel_dp_is_edp(struct drm_device *dev, enum port port)
 		[PORT_E] = DVO_PORT_DPE,
 	};
 
+	/*
+	 * eDP not supported on g4x. so bail out early just
+	 * for a bit extra safety in case the VBT is bonkers.
+	 */
+	if (INTEL_INFO(dev)->gen < 5)
+		return false;
+
 	if (port == PORT_A)
 		return true;