Ch32 v307 kconfig fix (#6373)
Ch32 v307 kconfig fix (#6373)

* add Kconfig file "USART2~USART8"
RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread,RT-Thread/rt-thread