Revert "allow override of cabc file via property"

A quick search reveals that only 1 device uses this - kona.

Instead of adding a system prop for this, that one device
can add its own AdaptiveBacklight class. This allows kona to
use AdaptiveBacklight without having to modify the common class.

This reverts commit c11396ec.

Change-Id: Id912091f64da39a10d30c9770f248cf6467e8760