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>
diff --git a/src/gpu/mtl/GrMtlCaps.h b/src/gpu/mtl/GrMtlCaps.h
index 6de830d..6eb775c 100644
--- a/src/gpu/mtl/GrMtlCaps.h
+++ b/src/gpu/mtl/GrMtlCaps.h
@@ -80,6 +80,11 @@
         return false;
     }
 
+    bool getYUVAConfigFromBackendTexture(const GrBackendTexture&,
+                                         GrPixelConfig*) const override {
+        return false;
+    }
+
     bool getYUVAConfigFromBackendFormat(const GrBackendFormat&,
                                         GrPixelConfig*) const override {
         return false;