drm: Check for connection_mutex in drm_select_eld

drm_select_eld should check for mode_config.connection_mutex as
well as mode_config.mutex: We need that since this function checks
conector->encoder links.

Signed-off-by: Sean Paul <seanpaul@chromium.org>
[danvet: Pimp commit message slightly.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
diff --git a/drivers/gpu/drm/drm_edid.c b/drivers/gpu/drm/drm_edid.c
index dfa9769..087d608 100644
--- a/drivers/gpu/drm/drm_edid.c
+++ b/drivers/gpu/drm/drm_edid.c
@@ -3305,6 +3305,7 @@
 	struct drm_device *dev = encoder->dev;
 
 	WARN_ON(!mutex_is_locked(&dev->mode_config.mutex));
+	WARN_ON(!drm_modeset_is_locked(&dev->mode_config.connection_mutex));
 
 	list_for_each_entry(connector, &dev->mode_config.connector_list, head)
 		if (connector->encoder == encoder && connector->eld[0])