stm32/mboot: Add support for 4th board LED.
stm32/mboot: Add support for 4th board LED.

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