linux-ramdump-parser-v2: Use a more generic function for rtb parsing

Commit 4eb3aa20
(linux-ramdump-parser-v2: Update RTB for 64-bit) added support for
64-bit RTB parsing but broke backwards compatibility for old branches
that don't have the 64-bit changes. Update the parser to support
both old and new formats.

Change-Id: I6b9d834e1073d97dd3ffe43c1cc1f753d40e91b8