atusb/fw/board_app.c: do not read and accumulate IRQs; flash LED when EP1 busy
atusb/fw/board_app.c: do not read and accumulate IRQs; flash LED when EP1 busy

To indicate an interrupt, we just send a zero byte.

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