packages: libusb: add package 'fxload' (from libusb examples)

packages: libusb: add package 'fxload' (from libusb examples)

The 'fxload' tool contained in the examples provided with libusb is
actually useful and turns out to be the only way to load firmware into
some rather ancient EZ-USB microcontrollers made by Cypress (formerly
Anchor Chips).
The original 'fxload' tool from hotplug-linux has been abandonned long
ago and requires usbfs to be mounted in /proc/bus/usb/ (like it was in
Linux 2.4...).
Hence the best option is to package the modern 'fxload' from the libusb
examples which (unsurprisingly) uses libusb and works on modern
systems.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>