- KNF cleanup.

- KNF cleanup.
- Add support for memory mapped I/O.
- Use DMA to get SCBs down to the adapters.
- Remove old paging code.
- Be much smarter about how we allocate SCB space.  The old, simple method
  wasted almost half a page per SCB. Ooops.
- Make command complete interrupt processing more efficient.
- Break the monolithic ahc_intr into sub-routines.  The sub-routines handle
  rare, special case events so the function call is not a penalty and the
  removal of the code from the main routine most likely improves performance
  instruction prefech will work better and less code is pushed into the cache.
- Never, ever allow tagged queueing if a device has disconnection disabled.
- Clean up and simplify timeout code.  Many of the changes are to handle the
  new DMA scheme.