The IRQ calculation for the virtio range was off by 8, which caused the
virtio code to override the interrupt registration for the RTC, which
caused it to stop firing. Clean up the #defines that define irq mappings
to fix this issue.
Uses the QEMU virt machine for 68k defined in qemu 6.0+.
Basic support that boots, prints to the console, takes input from
console, and context switches.
TODO: interrupt support, timer support.
