fix mips msa build w/CONFIG_EXT_TX

vp10_fht{16x16,8x8,4x4}_msa and the iht were disabled with this config
in:
4ab19ea Fix assertion failures in mips+msa setting

Change-Id: Ic675258b89ca490e8021c887b705c68428925129
diff --git a/test/dct16x16_test.cc b/test/dct16x16_test.cc
index d0e2b4b..d71bc86 100644
--- a/test/dct16x16_test.cc
+++ b/test/dct16x16_test.cc
@@ -921,6 +921,7 @@
                         ::testing::Values(make_tuple(&vpx_fdct16x16_msa,
                                                      &vpx_idct16x16_256_add_msa,
                                                      0, VPX_BITS_8)));
+#if !CONFIG_EXT_TX
 INSTANTIATE_TEST_CASE_P(
     MSA, Trans16x16HT,
     ::testing::Values(make_tuple(&vp10_fht16x16_msa, &vp10_iht16x16_256_add_msa,
@@ -931,6 +932,7 @@
                                  2, VPX_BITS_8),
                       make_tuple(&vp10_fht16x16_msa, &vp10_iht16x16_256_add_msa,
                                  3, VPX_BITS_8)));
+#endif  // !CONFIG_EXT_TX
 INSTANTIATE_TEST_CASE_P(MSA, PartialTrans16x16Test,
                         ::testing::Values(make_tuple(&vpx_fdct16x16_1_msa,
                                                      VPX_BITS_8)));