kevin: Don't charge from source ports
kevin: Don't charge from source ports

BC1.2 detection may still occur on multi-purpose ports which we are
currently sourcing. Don't charge from such ports, and don't incorrectly
indicate that external power is present.

BUG=chrome-os-partner:55907
BRANCH=None
TEST=Manual on kevin, plug Apple charge-thru accessory with no charger
attached, verify we don't charge from it.

Change-Id: I9a74f1123fc51c7fc622f985bd528e96b9526946
Signed-off-by: Shawn Nematbakhsh <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/378595
Commit-Ready: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Tested-by: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Reviewed-by: Aseda Aboagye <12c9b286316a940fd31c24070da5ab64cdd4d0e7@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec