disable vp9_iht16x16_256_add_neon

this causes test vector failures

BUG=webm:1403

Change-Id: Ifdb5b270c5cc70be5689e4fbda2ada3724cc65c3
diff --git a/test/dct_test.cc b/test/dct_test.cc
index 66b2add..a1440ca 100644
--- a/test/dct_test.cc
+++ b/test/dct_test.cc
@@ -636,7 +636,11 @@
 #endif
   { &vp9_fht4x4_c, &iht_wrapper<vp9_iht4x4_16_add_neon>, 4, 1 },
   { &vp9_fht8x8_c, &iht_wrapper<vp9_iht8x8_64_add_neon>, 8, 1 },
+// TODO(linfengz): reenable this function once test vector failures are
+// addressed.
+#if 0
   { &vp9_fht16x16_c, &iht_wrapper<vp9_iht16x16_256_add_neon>, 16, 1 }
+#endif
 };
 
 INSTANTIATE_TEST_CASE_P(
diff --git a/vp9/common/vp9_rtcd_defs.pl b/vp9/common/vp9_rtcd_defs.pl
index c705c5e..5dbe5a6 100644
--- a/vp9/common/vp9_rtcd_defs.pl
+++ b/vp9/common/vp9_rtcd_defs.pl
@@ -69,7 +69,7 @@
   # CONFIG_VP9_HIGHBITDEPTH is off.
   specialize qw/vp9_iht4x4_16_add neon sse2/;
   specialize qw/vp9_iht8x8_64_add neon sse2/;
-  specialize qw/vp9_iht16x16_256_add neon sse2/;
+  specialize qw/vp9_iht16x16_256_add sse2/;
   if (vpx_config("CONFIG_VP9_HIGHBITDEPTH") ne "yes") {
     # Note that these specializations are appended to the above ones.
     specialize qw/vp9_iht4x4_16_add dspr2 msa/;