Modify EC software sync to update RO if necessary

Allow the AP to sync and verify the EC read only image after updating
the rewritable image.

BUG=chrome-os-partner:48703
BRANCH=none
TEST=manual

1. Update EC to a new version
2. rebuild EC code
3. Update AP firmware
4. Reboot and check that the RO image is updated after the RW image is
updated.

CQ-DEPEND=CL:319213

Change-Id: I774ef25320103f20d8c7d1c180a220dd0819c04d
Signed-off-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/320614
Reviewed-by: Randall Spangler <rspangler@chromium.org>
3 files changed