[Bug] libcpu/ppc 下有部分文件标识为 GPL，和 RT-Thread 的 Apache 授权冲突

### RT-Thread Version

master

### Hardware Type/Architectures

N/A

### Develop Toolchain

Other

### Describe the bug

搜索关键字 “General Public License”

- libcpu/ppc/ppc405/dcr_gcc.S
- libcpu/ppc/ppc405/include/asm/ppc_defs.h

### Other additional context

_No response_