dump_vpd_log: Add region to VPD whitelist.

BUG=chromium:306527
TEST=run dump_vpd_log --force --stdout and see region being displayed.

Change-Id: Ic597cbff9be777064a633a5403e2c3738031fec5
Reviewed-on: https://chromium-review.googlesource.com/172727
Reviewed-by: David Hendricks <dhendrix@chromium.org>
Reviewed-by: Yung-chieh Lo <yjlou@chromium.org>
Commit-Queue: Paul Stewart <pstew@chromium.org>
Tested-by: Paul Stewart <pstew@chromium.org>