Platform: x86: Add Chrome OS Laptop driver

This adds the chromeos_laptop driver. It supports
the Cypress APA SMBUS touchpad as well as the isl29018 i2c ambient
light sensor on the Samsung Series 5 550 Chromebook.

Signed-off-by: Benson Leung <bleung@chromium.org>
Reviewed-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Matthew Garrett <matthew.garrett@nebula.com>