dtc: Better exercise dtc base and bytestring features

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> This patch alters the main testcase, and the dts file corresponding to
> it so that we at least trivially exercise dtc's bytestring and base
> conversion features.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

jdl