[Bug] serial_fops_open 顺序错误导致 rx_indicate 被清空

### RT-Thread Version

5.2.2

### Hardware Type/Architectures

HPM6750

### Develop Toolchain

RT-Thread Studio

### Describe the bug

rt_serial_close() 关闭时清空回调
serial_fops_open() 先设回调，再 close/open
poll()/select() 阻塞等待控制台永不被唤醒

### Other additional context

_No response_