stm32/sdcard: Add hook for a board to power on SD/MMC.
stm32/sdcard: Add hook for a board to power on SD/MMC.

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