dtc: Add code to make diffing trees easier

[Jon Loeliger]

> This patch adds a "dtdiff" script to do a useful form diff of two
> device trees.  This automatically converts the tree to dts form (if
> it's not already) and uses a new "-s" option in dtc to "sort" the
> tree.  That is, it sorts the reserve entries, it sorts the properties
> within each node by name, and it sorts nodes by name within their
> parent.
> 
> This gives a pretty sensible diff between the trees, which will ignore
> semantically null internal rearrangements (directly diffing the dts
> files can give a lot of noise due to the order changes).
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

Thanks,
jdl