utils: eth_mac_addr: Refactor ethernet mac addr script am: e0b877ac38 am: 0ee1ffe493 am: 5bad9d4fe9 am: 5e09cf75fb am: 886811f2ad

Original change: https://android-review.googlesource.com/c/device/linaro/dragonboard/+/2664199

Change-Id: I117d5c7efb0d9b158069b73dcfe6d9a8fe5f02fd
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>