Add GBB flag to disable PD software sync

In order to disable PD software sync but still do EC software sync
it is useful to have a separate GBB flag for it.

This will allow me to release a Samus P2B firmware image that will
update the EC but not the PD, since the PD FW that comes on P2B
devices cannot be updated with software sync.

BUG=chrome-os-partner:30079
BRANCH=None
TEST=flash BIOS with updated EC+PD:
1) no GBB flags to override behavior updates both EC and PD
2) GBB flag to disable EC software sync disables both EC and PD update
3) GBB flag to disable PD software sync disables only PD update

Change-Id: I49ffb59238bee4a2dd66b24f2516e3ce46ea06cd
Signed-off-by: Duncan Laurie <dlaurie@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/211910
Reviewed-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-by: Randall Spangler <rspangler@chromium.org>
4 files changed