drm/nouveau: Use lockless gem BO free callback

No dev->struct_mutex anywhere to be seen.

Cc: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: NDaniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1464630800-30786-9-git-send-email-daniel.vetter@ffwll.ch

drivers/gpu/drm/nouveau/nouveau_drm.c

@@ -970,7 +970,7 @@ driver_stub = {
 	.gem_prime_vmap = nouveau_gem_prime_vmap,
 	.gem_prime_vunmap = nouveau_gem_prime_vunmap,
 
-	.gem_free_object = nouveau_gem_object_del,
+	.gem_free_object_unlocked = nouveau_gem_object_del,
 	.gem_open_object = nouveau_gem_object_open,
 	.gem_close_object = nouveau_gem_object_close,