drm/i915: don't save/restore LBB on Gen5+

Because this PCI config register doesn't exist on Gen5+.
Signed-off-by: NPaulo Zanoni <paulo.r.zanoni@intel.com>
Reviewed-by: NVille Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_suspend.c

@@ -340,7 +340,9 @@ int i915_save_state(struct drm_device *dev)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int i;
 
-	pci_read_config_byte(dev->pdev, LBB, &dev_priv->regfile.saveLBB);
+	if (INTEL_INFO(dev)->gen <= 4)
+		pci_read_config_byte(dev->pdev, LBB,
+				     &dev_priv->regfile.saveLBB);
 
 	mutex_lock(&dev->struct_mutex);
 
@@ -390,7 +392,9 @@ int i915_restore_state(struct drm_device *dev)
 	struct drm_i915_private *dev_priv = dev->dev_private;
 	int i;
 
-	pci_write_config_byte(dev->pdev, LBB, dev_priv->regfile.saveLBB);
+	if (INTEL_INFO(dev)->gen <= 4)
+		pci_write_config_byte(dev->pdev, LBB,
+				      dev_priv->regfile.saveLBB);
 
 	mutex_lock(&dev->struct_mutex);