hwc: Increase precision in triming

Increase precision from float to double in triming calcs.
This improves the output. We need this since ultimately
we assign to int which would truncate excesses. With float
due to lower precision, we end up slightly lower than an
integral value.

Change-Id: I5d781b609be1761b746edf6503340f34a985b9e2
1 file changed