dtc: import latest upstream dtc

[Jon Loeliger]

> 
> Seems dtc doesn't really have a maintainer. 

Picking nits, let's be clear on that phraseology:

    Seems dtc doesn't really have a maintainer
    within the kernel repository.

Over in git.jdl.com land, there is a well established
maintainer for the upstream DTC.

> Probably makes more sense
> for me to take this unless there are objections.

Please, and thank you.

jdl