dtc: Make -Idts -Odts preserve node/property labels

[Jon Loeliger]

So, like, the other day David Gibson mumbled:
> This patch changes -Odts mode output so that labels on properties,
> nodes and memreserve entries in input source are preserved in the
> output.
> 
> Preserving labels within property values is trickier - another patch
> coming later.
> 
> Signed-off-by: David Gibson <david at gibson.dropbear.id.au>

Applied.

jdl