More YUV cleanup

* Remove more uses of colortype
* Add back SkImage_GpuYUVA::MakeFromYUVATextures

Bug: skia:7903
Change-Id: I3ee119d190db39c128516dbb78db34fe29ba3cce
Reviewed-on: https://skia-review.googlesource.com/c/165943
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Jim Van Verth <jvanverth@google.com>
11 files changed