UML supports enabling OF, and is useful for running the device tree
tests, so add support for unflattening device tree blobs so we can
actually use it.
Signed-off-by: Brendan Higgins <brendanhiggins@google.com> Reviewed-by: Frank Rowand <frank.rowand@sony.com> Signed-off-by: Rob Herring <robh@kernel.org>