libfdt: More tests of NOP handling behaviour

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> In light of the recently discovered bug with NOP handling, this adds
> some more testcases for NOP handling.  Specifically, it adds a helper
> program which will add a NOP tag after every existing tag in a dtb,
> and runs the standard battery of tests over trees mangled in this way.
> 
> For now, this does not add a NOP at the very beginning of the
> structure block.  This causes problems for libfdt at present, because
> we assume in many places that the root node's BEGIN_NODE tag is at
> offset 0.  I'm still contemplating what to do about this (with one
> option being simply to declare such dtbs invalid).
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

BTW, declaring DTBs with BEGIN_NODES not at offset 0
as invalid seems like a fine choice to me.

jdl