cgpt: prioritize: Make sure all headers/entries are valid

The prioritize cmd expected primary gpt header and entries are valid.

Add a validity check to guarantee that.

BUG=b:35585016
TEST=Check on bob, the secondary gpt still valid after these commands:
dd if=/dev/zero of=/dev/mmcblk0 bs=512 count=64
cgpt prioritize /dev/mmcblk0

Change-Id: I853e25211a46fa3ce93cef1e5169b93b0a6430a9
Signed-off-by: Jeffy Chen <jeffy.chen@rock-chips.com>
Reviewed-on: https://chromium-review.googlesource.com/604814
Reviewed-by: Randall Spangler <rspangler@chromium.org>
Reviewed-by: Julius Werner <jwerner@chromium.org>
2 files changed