generic-arm64: Set device tree in dtb_service when present. am: 0aee8be560

Original change: https://android-review.googlesource.com/c/trusty/lk/trusty/+/3451186

Change-Id: I71eaf9202ab78a21d2e828df331cb20ac7e3b2d1
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>