atusb.brd: added two vias to connect front and back ground at USB shield
atusb.brd: added two vias to connect front and back ground at USB shield

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