Remove unused cctools code paths for old libusb and cp2103 ioctls.

Communication with the CP2103 board has gone through three revisions,
first using ioctls supported by the CP2103 kernel driver, then using
the old synchronous usb library and now using the newer libusb
asynchronous interface. There's no reason to keep shipping the old
stale code now that the new stuff works reliably.

Signed-off-by: Keith Packard <keithp@keithp.com>