Remove SkNx AVX code. It is not really used. Getting in the way of refactoring.

src/core/SkOpts.cpp

Index: src/core/SkOpts.cpp
diff --git a/src/core/SkOpts.cpp b/src/core/SkOpts.cpp
index 56604171bbe9629b77efe64c3919294e57fbde28..fbc4f6cd6243313a6670b8882b2807885200343c 100644
--- a/src/core/SkOpts.cpp
+++ b/src/core/SkOpts.cpp
@@ -94,7 +94,7 @@ namespace SkOpts {
     void Init_ssse3();
     void Init_sse41();
     void Init_sse42() {}
-    void Init_avx();
+    void Init_avx() {}
     void Init_avx2() {}
     void Init_neon();