stm32 cubemx hal dma uart参考例程，发送和接收

参考：
https://blog.csdn.net/toopoo/article/details/80012317
https://blog.csdn.net/morixinguan/article/details/94414622
https://blog.csdn.net/Wekic/article/details/83040285
https://blog.csdn.net/ouening/article/details/79252770