Update LANE_CENTERING_ASSIST_ENABLED documentation in HAL

     * drifts toward or over the lane marking. If an unintentional lane departure is detected, the

     * system applies steering control to return the vehicle into the current lane.

     *

     * In general, LANE_CENTERING_ASSIST_ENABLED should always return true or false. If the feature

     * is not available due to some temporary state, such as the vehicle speed being too low or too

     * high, that information must be conveyed through the ErrorState values in the

     * LANE_CENTERING_ASSIST_STATE property.

     *

     * This property is defined as read_write, but OEMs have the option to implement it as read

     * only.

     *