defconfig: vega: Enable DC fake battery detection.

This will ensure that in the lab environment, we do not try to
charge the power supplies that are used as fake batteries.

For normal batteries there is no change.

Bug: 111000040
Test: Real battery works as expected.
      For a fake battery, charging is disabled.

Change-Id: I093cba96170aad576bf756ebef080d709d56f213