Revert "platform/chrome: chromeos_laptop: make chromeos_laptop const"

This reverts commit a376cd91 because
chromeos_laptop instances should not be marked as "const" (at this
time), since i2c_peripheral is being modified (we change "state" and
"tries") when we instantiate devices.

Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Signed-off-by: Benson Leung <bleung@chromium.org>