stm32/adc: Add support for H7 MCU series.
stm32/adc: Add support for H7 MCU series.

ADC3 is used because the H7's internal ADC channels are connected to ADC3
and the uPy driver doesn't support more than one ADC.

Only 12-bit resolution is supported because 12 is hard-coded and 14/16 bits
are not recommended on some ADC3 pins (see errata).

Values from internal ADC channels are known to give wrong values at
present.

trezor/micropython,adafruit/circuitpython,adafruit/micropython,bvernoux/micropython,pramasoul/micropython,adafruit/circuitpython,kerneltask/micropython,kerneltask/micropython,henriknelson/micropython,pozetroninc/micropython,bvernoux/micropython,henriknelson/micropython,pfalcon/micropython,selste/micropython,dmazzella/micropython,dmazzella/micropython,kerneltask/micropython,tralamazza/micropython,pfalcon/micropython,tralamazza/micropython,swegener/micropython,pramasoul/micropython,MrSurly/micropython,swegener/micropython,tobbad/micropython,adafruit/micropython,pfalcon/micropython,kerneltask/micropython,tobbad/micropython,ryannathans/micropython,dmazzella/micropython,selste/micropython,adafruit/circuitpython,selste/micropython,ryannathans/micropython,adafruit/micropython,pramasoul/micropython,henriknelson/micropython,ryannathans/micropython,MrSurly/micropython,pfalcon/micropython,pozetroninc/micropython,bvernoux/micropython,swegener/micropython,ryannathans/micropython,pfalcon/micropython,tralamazza/micropython,henriknelson/micropython,adafruit/circuitpython,pramasoul/micropython,tobbad/micropython,swegener/micropython,adafruit/circuitpython,pozetroninc/micropython,henriknelson/micropython,MrSurly/micropython,MrSurly/micropython,trezor/micropython,swegener/micropython,tobbad/micropython,ryannathans/micropython,trezor/micropython,MrSurly/micropython,kerneltask/micropython,trezor/micropython,bvernoux/micropython,selste/micropython,trezor/micropython,dmazzella/micropython,tralamazza/micropython,pozetroninc/micropython,adafruit/micropython,bvernoux/micropython,pozetroninc/micropython,tobbad/micropython,selste/micropython,pramasoul/micropython,adafruit/micropython,adafruit/circuitpython