stm32/adc: Fix ADC reading on F0 MCUs to only sample a single channel.
stm32/adc: Fix ADC reading on F0 MCUs to only sample a single channel.

And increase sampling time to get better results for internal channels.

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