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

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

Change-Id: I61e796afcc35a871b4ade93965526d04dab37d1c
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>