duo/main.cpp: fix ExtInt initialization issue, if micropython performs a soft reset.
duo/main.cpp: fix ExtInt initialization issue, if micropython performs a soft reset.

ganshun666/micropython,ganshun666/micropython,ganshun666/micropython,redbear/micropython,redbear/micropython,redbear/micropython,redbear/micropython,ganshun666/micropython,redbear/micropython,ganshun666/micropython