Update switchable_interp_cdf once per frame.

Move from computing the switchable_interp_cdf per symbol to
 computing once per frame when the probabilities are adapted.

Change-Id: I6571126239f0327e22bb09ee8bad94114291683e

av1/decoder/decoder.c

@@ -47,6 +47,10 @@ static void initialize_dec(void) {
     av1_init_wedge_masks();
 #endif  // CONFIG_EXT_INTER
     init_done = 1;
+#if CONFIG_DAALA_EC
+    av1_indices_from_tree(av1_switchable_interp_ind, av1_switchable_interp_inv,
+                          SWITCHABLE_FILTERS, av1_switchable_interp_tree);
+#endif
   }
 }