stm32/mboot: Only compile in code for the USB periph that is being used.
stm32/mboot: Only compile in code for the USB periph that is being used.

Prior to this patch, if both USB FS and HS were enabled via the
configuration file then code was included to handle both of their IRQs.
But mboot only supports listening on a single USB peripheral, so this patch
excludes the code for the USB that is not used.

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