update wrong file name in rtdevice.h

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2343 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/drivers/include/rtdevice.h

 /*
- * File      : serial.h
+ * File      : rtdevice.h
  * This file is part of RT-Thread RTOS
  * COPYRIGHT (C) 2006 - 2012, RT-Thread Development Team
  *