device_tree: Switch to libpayload version

CB:77970 has made coreboot's version of the device tree code (which was
originally copied from depthcharge and is therefore practically
identical except for coding style) available in libpayload. This patch
removes depthcharge's version to make use of that instead.

BRANCH=none
BUG=none
TEST=Booted CoachZ

Cq-Depend: chromium:5649667
Change-Id: I26022003c40656a668b0812440614b2b97e24c8d
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/depthcharge/+/5655634
Reviewed-by: Yu-Ping Wu <yupingso@chromium.org>
Commit-Queue: Yu-Ping Wu <yupingso@chromium.org>
Tested-by: Yu-Ping Wu <yupingso@chromium.org>
27 files changed