Fix merge issues related  --enable-ec-adapt

1. Avoid compiler warnings.
2. Enable prob_diff_update() required by update_txfm_probs().

Change-Id: I9081b645c55a8432bdaeb600e9ba901c0d0d96f5
diff --git a/aom_dsp/prob.h b/aom_dsp/prob.h
index 28ea49c..9384ffe 100644
--- a/aom_dsp/prob.h
+++ b/aom_dsp/prob.h
@@ -33,7 +33,7 @@
 
 typedef int8_t aom_tree_index;
 
-#define TREE_SIZE(leaf_count) (2 * (leaf_count)-2)
+#define TREE_SIZE(leaf_count) (-2 + 2 * (leaf_count))
 
 #define aom_complement(x) (255 - x)