lib/atusb.c: fix typo in function name
lib/atusb.c: fix typo in function name

- lib/atusb.c (atusd_interrupt, atusb_driver): we're in atusb.c, so the
  function name should begin with atusb_, not atusd_

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