Disable dithering on the PowerVR GE8320

FWIW, our PowerVRGE8320 reports that it has integer shader support.

Bug: b/195281495
Change-Id: Ie969d8e978404a5b8963bb5c71dedfa8945b2a2e
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/436563
Commit-Queue: Robert Phillips <robertphillips@google.com>
Reviewed-by: Brian Salomon <bsalomon@google.com>
4 files changed