* 2021-8-25      SVCHAO       The baud rate is configured according to the different APB1 frequencies.
                               f4-series only.

        rt_uint16_t old_flag = _console_device->open_flag;

        _console_device->open_flag |= RT_DEVICE_FLAG_STREAM;
        rt_device_write(_console_device, 0, str, rt_strlen(str));
        _console_device->open_flag = old_flag;

        当一个线程正在执行 rt_device_write(_console_device, 0, str, rt_strlen(str));函数时，一个高优先级线程
抢占当前线程并修改 _console_device->open_flag（修改为RT_DEVICE_FLAG_INT_RX，之前不是中断接收），
高优先级线程执行完后，继续执行以前线程，此时old_flag与_console_device->open_flag不一致，执行
_console_device->open_flag = old_flag;后_console_device->open_flag新的值被覆盖。控制台串口实际配置
成硬件中断接收，因为_console_device->open_flag值被修改为不是中断，最后导致控制台串口无法接收任何数据
输入。

[lts 3.1.x] format codes

[lts-3.1.x]update ChangeLog.md

[lts-3.1.x][src]移除 c99 依赖

[lts-3.1.x][bsp]移除 stmf20x

[lts-3.1.x][bsp] imx6ul bsp sync from master

[lts-3.1.x]delete gpl files

[lts-3.1.x][libcpu]update GPL license to Apache-2.0

[lts-3.1.x][bsp] remove zynq7000 bsp

[lts-3.1.x][components]update GPL license to Apache-2.0

[lts-3.1.x][bsp]update GPL license to Apache-2.0, and format license

[Update] Sync from v4.0.3

fixed scons --dist in IMXRT BSP

update change log.