drm/rcar-du: Use lockless gem BO free callback

No dev->struct_mutex anywhere to be seen.

Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1464630800-30786-11-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/rcar-du/rcar_du_drv.c

@@ -217,7 +217,7 @@ static struct drm_driver rcar_du_driver = {
 	.get_vblank_counter	= drm_vblank_no_hw_counter,
 	.enable_vblank		= rcar_du_enable_vblank,
 	.disable_vblank		= rcar_du_disable_vblank,
-	.gem_free_object	= drm_gem_cma_free_object,
+	.gem_free_object_unlocked = drm_gem_cma_free_object,
 	.gem_vm_ops		= &drm_gem_cma_vm_ops,
 	.prime_handle_to_fd	= drm_gem_prime_handle_to_fd,
 	.prime_fd_to_handle	= drm_gem_prime_fd_to_handle,