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@gibson.dropbear.id.au>