altoslib: When flashing hardware, pull USB data from device if needed

If we fail to extract USB vid/pid and product values from the device
ROM, use the data discovered over USB when the device was originally
discovered.

Also, use the USB product to select appropriate .ihx files instead of
only using the USB vid/pid. This will help people avoid using the
wrong file when reflashing devices.

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