greatfet-firmware: allow selection of device by index
greatfet-firmware: allow selection of device by index

greatscottgadgets/greatfet,dominicgs/GreatFET-experimental,greatscottgadgets/greatfet,dominicgs/GreatFET-experimental,greatscottgadgets/greatfet,greatscottgadgets/greatfet,dominicgs/GreatFET-experimental