CPUs by default, and provide a functional version of BUS_BIND_INTR().
While here, fix some potential concurrency problems in the interrupt
handling code.
Powermac G5 systems. MSI and several other things are not presently
supported.
The U3/U4 internal device support portions of this change were contributed
by Andreas Tobler.
MFC after: 1 week
provided, for example, on the PowerPC 970 (G5), as well as on related CPUs
like the POWER3 and POWER4.
This also adds support for various built-in hardware found on Apple G5
hardware (e.g. the IBM CPC925 northbridge).
Reviewed by: grehan