Fix compiler warning

Use llabs to handle 64-bit integer.

Change-Id: I6b3f3400228311ab11b594f12880e80e9b17d740
diff --git a/av1/encoder/encodeframe.c b/av1/encoder/encodeframe.c
index c1bbb7c..8756531 100644
--- a/av1/encoder/encodeframe.c
+++ b/av1/encoder/encodeframe.c
@@ -4489,8 +4489,8 @@
     if (idx > 2 && !is_overlay) {
       // If the predictive coding gains are smaller than the previous more
       // relevant frame over certain amount, discard this frame.
-      if (labs(inter_cost[rank_index[idx]]) <
-              labs(inter_cost[rank_index[idx - 1]]) / 8 ||
+      if (llabs(inter_cost[rank_index[idx]]) <
+              llabs(inter_cost[rank_index[idx - 1]]) / 8 ||
           inter_cost[rank_index[idx]] == 0)
         cutoff_ref = 1;