Fix valgrind warning

This commit adds initialization for tmp_rd_stats, to resolve valgrind
warning of "Conditional jump or move depends on uninitialised value"

Change-Id: I79ed3bc046a66457c27185782645938d223872ba

av1/encoder/rdopt.c

diff --git a/av1/encoder/rdopt.c b/av1/encoder/rdopt.c
index 54b40b6..85a90d7 100644
--- a/av1/encoder/rdopt.c
+++ b/av1/encoder/rdopt.c
@@ -9203,6 +9203,8 @@
           int_mv cur_mv;
           RD_STATS tmp_rd_stats, tmp_rd_stats_y, tmp_rd_stats_uv;
 
+          av1_invalid_rd_stats(&tmp_rd_stats);
+
           mbmi->ref_mv_idx = 1 + ref_idx;
 
           for (ref = 0; ref < 1 + comp_pred; ++ref) {