STM32F401 has USART6 on PA12/PA11 and PC7/PC6 with alternate
function mapping AF08. This can be used, for example, to connect
to the Elegoo Neptune 3, where PA12/PA11 are wired to an RJ10 plug
going to the stock screen.
Signed-off-by: Marius Petcu <marius@petcu.me>