altos/drivers: Pads with multi-port firing and pad selector DIP switch

TeleFire 8 scrambles GPIOs to make layout cleaner, placing the 8
firing outputs across two GPIO ports.

We're also adding an 8-unit selector for box number so that boards can
be re-configured in the field. These override any ROM-configuration
value; you can select the rom value by setting all switches to 'off'.

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