Move common logic into a default routine in platform/power that other
platforms can reuse to implement the general default shutdown logic.
Add helper routines to print the cause.
Refactor the platforms that had substantial halt logic to reuse the
default implementation.
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.
Port to the really neat 68010 based board at https://rosco-m68k.com/
Port Features:
-10Mhz 68010
-1MB ram
-Dual UART + timer implemented as a 68c681 chip
-timer running at 1Khz, UART A for console
-interrupt driven RX support
Some amount of extending of the 68k exceptinon code was needed to
support the autovectored irqs that the 68681 uart uses. Added build
system support for 68010.
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.
