depthcharge: Notify EC of current boot mode

1. Sync two new EC APIs from EC source.
   - EC_CMD_SB_FW_UPDATE
   - EC_CMD_ENTERING_MODE

2. Implemented vboot API, VbExEcEnteringMode
   In order to Notify EC of boot mode,
   i.e. normal, developer or recovery.
   This is necessary for battery firmware updates.

BUG=chrome-os-partner:24741
CQ-DEPEND=CL:214249
CQ-DEPEND=CL:214273
BRANCH=ToT
TEST=Verified on glimmer

Change-Id: Ib82cc997da5dac6396cfe071e10b81b13c755670
Signed-off-by: Sheng-Liang Song <ssl@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/214253
Reviewed-by: Randall Spangler <rspangler@chromium.org>
5 files changed