Remove usage of $[ for arithmetic, take 2

I did a similar change in I8ba180be036836f37ebdbb6da36ff0be486c043e
but I guess somehow missed these ... maybe I forgot to add them to the
change.

As described originally, this causes TOT bashate to fail, so fix this
up before it gets released.

Change-Id: I5580cb46f1c8bd71c631549aab78428d95a6dc51
Merge "Remove usage of $[ for arithmetic, take 2"