Port MTD structures to use 64-bit byte offsets instead of sectors.

As per the discussion on issue 221745 we will be using 64-bit byte offsets
for the MTD partition table and converting to/from sectors internally in cgpt.
Existing interfaces do not change, eg sizes are still reported in sectors, only
the on-disk representation is affected.

BRANCH=none
BUG=chromium:221745
TEST=unit tests pass

Change-Id: Id312d42783acfdabe6eb8aea11dcbd298e00a100
Reviewed-on: https://gerrit.chromium.org/gerrit/60919
Commit-Queue: Albert Chaulk <achaulk@chromium.org>
Reviewed-by: Albert Chaulk <achaulk@chromium.org>
Tested-by: Albert Chaulk <achaulk@chromium.org>
7 files changed