- Merge from r249476: Ensure that PCI bus BUS_GET_DMA_TAG() method sees
  the actual PCI device which makes the request for DMA tag, instead of
  some descendant of the PCI device, by creating a pass-through trampoline.
- Sprinkle const on tables.
- Use NULL instead of 0 for pointers.
- Take advantage of nitems().

MFC after:	1 week