Disable Neon optimization of bad S32A/D565 blend.

BUG=skia:2797
R=mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/497823002
diff --git a/src/opts/SkBlitRow_opts_arm_neon.cpp b/src/opts/SkBlitRow_opts_arm_neon.cpp
index c486533..45b1a19 100644
--- a/src/opts/SkBlitRow_opts_arm_neon.cpp
+++ b/src/opts/SkBlitRow_opts_arm_neon.cpp
@@ -1649,7 +1649,11 @@
 const SkBlitRow::Proc sk_blitrow_platform_565_procs_arm_neon[] = {
     // no dither
     S32_D565_Opaque_neon,
+#if 0
     S32_D565_Blend_neon,
+#else
+    NULL,  // https://code.google.com/p/skia/issues/detail?id=2797
+#endif
     S32A_D565_Opaque_neon,
 #ifdef SK_CPU_ARM64
     NULL,   // https://code.google.com/p/skia/issues/detail?id=2845