Simplify selection to inverse-transform function

Change-Id: Ie45f96c21f0276f464cad3c7f69ac3dceed50c67
diff --git a/av1/common/idct.c b/av1/common/idct.c
index 8d2e92b..0e0834c 100644
--- a/av1/common/idct.c
+++ b/av1/common/idct.c
@@ -2502,18 +2502,17 @@
     case ADST_DCT:
     case DCT_ADST:
     case ADST_ADST:
-      av1_inv_txfm2d_add_4x4(input, CONVERT_TO_SHORTPTR(dest), stride, tx_type,
-                             bd);
-      break;
 #if CONFIG_EXT_TX
     case FLIPADST_DCT:
     case DCT_FLIPADST:
     case FLIPADST_FLIPADST:
     case ADST_FLIPADST:
     case FLIPADST_ADST:
+#endif  // CONFIG_EXT_TX
       av1_inv_txfm2d_add_4x4(input, CONVERT_TO_SHORTPTR(dest), stride, tx_type,
                              bd);
       break;
+#if CONFIG_EXT_TX
     case V_DCT:
     case H_DCT:
     case V_ADST:
@@ -2608,18 +2607,17 @@
     case ADST_DCT:
     case DCT_ADST:
     case ADST_ADST:
-      av1_inv_txfm2d_add_8x8(input, CONVERT_TO_SHORTPTR(dest), stride, tx_type,
-                             bd);
-      break;
 #if CONFIG_EXT_TX
     case FLIPADST_DCT:
     case DCT_FLIPADST:
     case FLIPADST_FLIPADST:
     case ADST_FLIPADST:
     case FLIPADST_ADST:
+#endif  // CONFIG_EXT_TX
       av1_inv_txfm2d_add_8x8(input, CONVERT_TO_SHORTPTR(dest), stride, tx_type,
                              bd);
       break;
+#if CONFIG_EXT_TX
     case V_DCT:
     case H_DCT:
     case V_ADST:
@@ -2646,18 +2644,17 @@
     case ADST_DCT:
     case DCT_ADST:
     case ADST_ADST:
-      av1_inv_txfm2d_add_16x16(input, CONVERT_TO_SHORTPTR(dest), stride,
-                               tx_type, bd);
-      break;
 #if CONFIG_EXT_TX
     case FLIPADST_DCT:
     case DCT_FLIPADST:
     case FLIPADST_FLIPADST:
     case ADST_FLIPADST:
     case FLIPADST_ADST:
+#endif  // CONFIG_EXT_TX
       av1_inv_txfm2d_add_16x16(input, CONVERT_TO_SHORTPTR(dest), stride,
                                tx_type, bd);
       break;
+#if CONFIG_EXT_TX
     case V_DCT:
     case H_DCT:
     case V_ADST: