Utils: Fix a bug in the linear transformation code.

Hand merge from ics-aah

> Utils: Fix a bug in the linear transformation code.
>
> Fix a bug where an incorrect result would be computed if you used the
> linear transformation code to do a reverse transformation (from B's
> domain into A's domain) when the scaler fraction was negative.
>
> Change-Id: I8e5f109314d235a177ab41f65d3c4cd08cff78be
> Signed-off-by: John Grossman <johngro@google.com>

Change-Id: Id90e18f685c61c1a89fd91c32adcf01363b3e8f3
Signed-off-by: John Grossman <johngro@google.com>