Update intra_ext_tx_cdf per frame.

Move computing the intra_ext_tx_cdf tables per symbol to
 computing them only when the probabilities are updated.

Change-Id: I26d5e419e103093e98a7d896c196176305b50fc9

av1/decoder/decoder.c

@@ -50,6 +50,8 @@ static void initialize_dec(void) {
 #if CONFIG_DAALA_EC
     av1_indices_from_tree(av1_switchable_interp_ind, av1_switchable_interp_inv,
                           SWITCHABLE_FILTERS, av1_switchable_interp_tree);
+    av1_indices_from_tree(av1_ext_tx_ind, av1_ext_tx_inv, TX_TYPES,
+                          av1_ext_tx_tree);
 #endif
   }
 }