drm/i915: backlight combination mode bit is gen4 only

Not valid for later non-PCH split platforms such as VLV.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/i915/intel_panel.c b/drivers/gpu/drm/i915/intel_panel.c
index 3bc89a6..8f025c6 100644
--- a/drivers/gpu/drm/i915/intel_panel.c
+++ b/drivers/gpu/drm/i915/intel_panel.c
@@ -329,7 +329,7 @@
 {
 	struct drm_i915_private *dev_priv = dev->dev_private;
 
-	if (INTEL_INFO(dev)->gen >= 4)
+	if (IS_GEN4(dev))
 		return I915_READ(BLC_PWM_CTL2) & BLM_COMBINATION_MODE;
 
 	if (IS_GEN2(dev))