qdev: enable vmstate_unregister() support

Now vmstate_unregister have the right type
Signed-off-by: NJuan Quintela <quintela@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

hw/qdev.c

@@ -296,10 +296,8 @@ void qdev_free(DeviceState *dev)
             bus = QLIST_FIRST(&dev->child_bus);
             qbus_free(bus);
         }
-#if 0 /* FIXME: need sane vmstate_unregister function */
         if (dev->info->vmsd)
             vmstate_unregister(dev->info->vmsd, dev);
-#endif
         if (dev->info->exit)
             dev->info->exit(dev);
         if (dev->opts)