Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Use BUS_DMA_COHERENT.

- Better use of the busdma API.
- Use spin locks instead of sleep locks.

Import dummy drivers for the i80321 DMA controller and AAU.
The DMA controller driver only knows how to do memory to memory copies, and
the AAU driver how to zero a chunk of memory.
Use them to process big (>=1KB) copying/zeroing.