dtb_service: Add setter and getter for device tree. am: d6b5562fbb Original change: https://android-review.googlesource.com/c/trusty/lk/trusty/+/3451184 Change-Id: If7dd8e754276c8f88bb4cdcfd2cbc4575ec06d6a Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>