Re: dtc: Add missing copyright notice for dumptrees.c

So, like, the other day David Gibson mumbled:

When I released libfdt, I forgot to add a copyright notice to
dumptrees.c (probably because the program is so trivial).  Apparently
the lack causes trouble for Debian, so this patch adds one.  I've gone
through the git history and double checked that no-one has touched
this file except me (and I barely have myself since its initial
commit).

Signed-off-by: David Gibson <redacted>

Applied.

jdl