Bootimage header size for header version 2 was being populated
incorrectly. Also, throw an error when an unsupported boot header
version is passed in as an argument.
Test: can see correct header size using unpack_bootimg.py
Bug: 111136242
Change-Id: Ia4ed7b2469a5296546627c91f441c496d67f5ce3
Boot image with header version 2 supports inclusion of
DTB image within the boot image.
Bug: 111136242
Test: unpack_bootimg.py is able to extract DTB added by
mkbootimg.py
Change-Id: Ie6ae2507aa0c1960c73077d618aacafb83ae8459