替换RTThread旧版文件头注释版权声明 (#5774)

libcpu/ppc/common/stack.c

@@ -1,15 +1,11 @@
 /*
- * File      : stack.c
- * This file is part of RT-Thread RTOS
- * COPYRIGHT (C) 2006-2021, RT-Thread Development Team
+ * Copyright (c) 2006-2022, RT-Thread Development Team
  *
- * The license and distribution terms for this file may be
- * found in the file LICENSE in this distribution or at
- * http://www.rt-thread.org/license/LICENSE
+ * SPDX-License-Identifier: Apache-2.0
  *
  * Change Logs:
  * Date           Author       Notes
- * 2011-02-14     Fred         first implementation for
+ * 2011-02-14     Fred         the first version
  */
 
 #include <rtthread.h>