libfdt: Test on trees with different block layouts

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> At present, all the example dtbs we use in the testsuite are version
> 17 and have reservation map, then structure block then strings block
> (the natural ordering based on alignment constraints).  However, all
> libfdt's read-only and in-place write functions should also work on
> v16 trees, and on trees with other layouts.
> 
> This patch adds a testcase / utility function to rearrange the blocks
> of a dtb and/or regress a v17 tree to v16, and uses it to run tests on
> trees with different layouts and versions.
> 
> Signed-off-by: David Gibson <david at tgibson.dropbear.id.au>

Applied.

jdl