drm/qxl: Don't take dev->struct_mutex in bo_force_delete

It really doesn't protect anything which doesn't have other locks
already. It also doesn't seem to be wired up into the driver unload
code fwiw, but that's a different issue.
Reviewed-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>

drivers/gpu/drm/qxl/qxl_object.c

@@ -272,7 +272,6 @@ void qxl_bo_force_delete(struct qxl_device *qdev)
 		return;
 	dev_err(qdev->dev, "Userspace still has active objects !\n");
 	list_for_each_entry_safe(bo, n, &qdev->gem.objects, list) {
-		mutex_lock(&qdev->ddev->struct_mutex);
 		dev_err(qdev->dev, "%p %p %lu %lu force free\n",
 			&bo->gem_base, bo, (unsigned long)bo->gem_base.size,
 			*((unsigned long *)&bo->gem_base.refcount));
@@ -280,8 +279,7 @@ void qxl_bo_force_delete(struct qxl_device *qdev)
 		list_del_init(&bo->list);
 		mutex_unlock(&qdev->gem.mutex);
 		/* this should unref the ttm bo */
-		drm_gem_object_unreference(&bo->gem_base);
-		mutex_unlock(&qdev->ddev->struct_mutex);
+		drm_gem_object_unreference_unlocked(&bo->gem_base);
 	}
 }