probe-serial.c does not work on /dev/ttyACM0

[Kay Sievers]

Hi Pierre,
did you test the serial prober with anything but plain old serial
ports? I seems to fail with serial USB devices, common in mobile
phones:
   open("/dev/ttyACM0", O_RDONLY|O_NONBLOCK|O_LARGEFILE) = 3
   ioctl(3, TIOCGSERIAL, 0xbff5029c) = -1 EINVAL (Invalid argument)

Thanks,
Kay