Use mad() for multiply-adds.

This generates smaller and hopefully slightly faster code.

Change-Id: I5343a3e8ca71f977698a0c11589ee39f95f11965
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/658922
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Herb Derby <herb@google.com>
1 file changed