- Re-write OF_decode_addr() with a bus-neutral approach, adding support

- Re-write OF_decode_addr() with a bus-neutral approach, adding support
  for nodes hanging off of Central (untested), FireHose (untested) and
  PCI (tested) busses.
- Add an additional parameter to OF_decode_addr() which specifies the
  index of the register bank to decode.

These should allow to eventually add support for the Z8530 hanging off of
FireHose to uart(4) and to write support for PCI-based graphics adapters.

Suggested by:	tmm (back in '03)