update: consolidated flat device tree code

[Paul Mackerras]

Hollis Blanchard writes:

> Still haven't looked to merge Matt's changes (because I'm busy, the
> current code works for me, and they haven't been accepted in u-boot
> yet).

The other version that was posted had support for modifying an
existing flat tree, which I need for the wrapper code for prep.  Are
those "Matt's changes"?  Are you thinking of adding that capability to
your version?

Paul.