Merge Perforce changeset 219925 to head:

Merge Perforce changeset 219925 to head:

  Provided a bus_space implementation for FDT, modelled on
  bus_space_generic, but with a local version of the map address
  routine that does a P->V translation, as is the case with NLM's
  similar routine for XLP.  It's not clear to me that this is the
  right solution -- possibly this belongs in simplebus -- however,
  it is sufficient to get the DE4 LED driver working.

Sponsored by:	DARPA, AFRL