PBUS bugs smashed

[Ulf Carlsson <ulfc@bun.falkenberg.se>]

Hi,

I can happily report perfect sound in my Indy. :-)

The last bug was quite tricky. I had to reboot the machine after every playback,
otherwise I got noise in the DMA channels.

I could obviously not set the configuration bits in the pbus ctrl register at
the same write as I wrote the activation bits..

- Ulf