tools/atrf-gpio/atusb.c: various bug fixes and improvements
tools/atrf-gpio/atusb.c: various bug fixes and improvements

- atusb.c (name): clarified that PC3 is unconnected
- atusb.c (gpio): "dir" and "data" were swapped
- atusb.c (gpio): complain if ATUSB_GPIO returns the wrong amount of data
- atusb.c (dump, main): show the pin configuration as well
- atusb.c (dump): show "-" for values where we don't expect a specific
  result
- atusb.c (dump): removed extra newline on mismatch

cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan,cfriedt/ben-wpan