i915: fix unneeded locking in i915 LVDS get modes code.

This code is always called under the lock from the higher layers,
so need to go locking it here.
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/i915/intel_lvds.c

@@ -311,10 +311,8 @@ static int intel_lvds_get_modes(struct drm_connector *connector)
 	if (dev_priv->panel_fixed_mode != NULL) {
 		struct drm_display_mode *mode;
 
-		mutex_lock(&dev->mode_config.mutex);
 		mode = drm_mode_duplicate(dev, dev_priv->panel_fixed_mode);
 		drm_mode_probed_add(connector, mode);
-		mutex_unlock(&dev->mode_config.mutex);
 
 		return 1;
 	}