cros_ec: Implement I2C pass-through

The Chrome EC has a feature where you can access its I2C buses through a
pass-through arrangement. Add a command to support this, and export the
function for it also.

Reviewed-by: Vadim Bendebury <vbendeb@google.com>
Signed-off-by: Simon Glass <sjg@chromium.org>
2 files changed