drm/msm: fix deadlock in bo create fail path

We already hold struct_mutex here.
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_gem.c

@@ -644,7 +644,7 @@ struct drm_gem_object *msm_gem_new(struct drm_device *dev,
 
 fail:
 	if (obj)
-		drm_gem_object_unreference_unlocked(obj);
+		drm_gem_object_unreference(obj);
 
 	return ERR_PTR(ret);
 }