stm32/modmachine: Fix reset_cause to correctly give DEEPSLEEP on L4 MCU.
stm32/modmachine: Fix reset_cause to correctly give DEEPSLEEP on L4 MCU.

Before this fix it returned SOFT_RESET after waking from a deepsleep
(standby).

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