utils: bdaddr: Fallback to bootconfig to read serialno am: bd160522bf am: deb54abc27 am: 68b9830dda am: 66ebf1e5bc

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

Change-Id: I61ca2b60222a7519ddbec863c9fc92225038590e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>