internal ethernet on the Quadra/Centris 660av/840av.
Add initial support for the PSC (DMA controller) to support the above
(DMA SCSI remains unsupported). This involved also changing the way
that several interrupts are handled.
Above from David Huang <khym@bga.com>
Since the interrupts changed somewhat, we must also make the ipls
dynamic, defaulting to their prior levels and adjusted for the AVs.
I modelled this on the hp300.
