Support DT compression using zlib/gzip

When using a DTBO header of version 1, the four least
significant bits of the flags field in dt_table_entry
will indicate the compression format of the DT entry.
Currently zlib and gzip compressions are supported.

Bug: 109892148
Test: make
Change-Id: Ie880c4508b5dd71ccf7725b06489b8701431bcb2