extmod/machine_signal: Fix parsing of invert arg when Pin is first arg.
extmod/machine_signal: Fix parsing of invert arg when Pin is first arg.

SHA2017-badge/micropython-esp32,SHA2017-badge/micropython-esp32,SHA2017-badge/micropython-esp32,SHA2017-badge/micropython-esp32,SHA2017-badge/micropython-esp32