Convert mkdtboimg.py to python 3

I was not able to test mkdtboimg_acpi_testdata.sh, because
aosp/1391197 appears to have broken mkdtboimg.py when
--version 2 is passed (or anything other than 0/1).

Bug: 203436762
Test: ./mkdtboimg_testdata.sh
Change-Id: I818f9124a3680c7a64935fd406756880e1ddc6c2
4 files changed