simplify loop in updateTextureCoordinates

Change-Id: I436da4596c9bb24c5ab1fb5c11edba47e8664d65
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/293837
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
2 files changed