stm32/uart: Add RTS/CTS pin configuration support to UART4.
stm32/uart: Add RTS/CTS pin configuration support to UART4.

selste/micropython,selste/micropython,trezor/micropython,pozetroninc/micropython,henriknelson/micropython,MrSurly/micropython,MrSurly/micropython,pramasoul/micropython,tobbad/micropython,adafruit/circuitpython,kerneltask/micropython,pramasoul/micropython,selste/micropython,bvernoux/micropython,kerneltask/micropython,pozetroninc/micropython,MrSurly/micropython,pozetroninc/micropython,pramasoul/micropython,bvernoux/micropython,pozetroninc/micropython,bvernoux/micropython,henriknelson/micropython,kerneltask/micropython,henriknelson/micropython,MrSurly/micropython,MrSurly/micropython,henriknelson/micropython,pramasoul/micropython,selste/micropython,tobbad/micropython,kerneltask/micropython,bvernoux/micropython,adafruit/circuitpython,trezor/micropython,bvernoux/micropython,trezor/micropython,adafruit/circuitpython,tobbad/micropython,pozetroninc/micropython,adafruit/circuitpython,tobbad/micropython,henriknelson/micropython,adafruit/circuitpython,pramasoul/micropython,trezor/micropython,adafruit/circuitpython,tobbad/micropython,trezor/micropython,kerneltask/micropython,selste/micropython