Function usb_debug

payloads/libpayload/include/usb/usb.h:347–355

#define USB_QUIRK_NONE				 0

static inline void __printf(1, 2) usb_debug(const char *fmt, ...)
{
#ifdef USB_DEBUG
	va_list ap;
	va_start(ap, fmt);
	vprintf(fmt, ap);
	va_end(ap);
#endif
}

/**
 * To be implemented by libpayload-client. It's called by the USB