utils: bdaddr: Fallback to bootconfig to read serialno am: bd160522bf am: deb54abc27 am: 68b9830dda

Original change: https://android-review.googlesource.com/c/device/linaro/dragonboard/+/2664198

Change-Id: I87a12e7d142f1d3a7d1b56b37e81fea5066eb8da
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>