Add a RX to the debug uart to STM32
As today the pin PC4 can be used as a TX for debug UART. All pins that can be used as a RX are occupied with other functions. But if P1V8_EN is moved from PC5 to another pin like PC2 or PC3 (both are free), then the TX/RX UART for the debug could be used. Please also consider mounting a connector for it.