Use RD_STATS for interp rd params

Replaced the stat variables of rate, dist, skip, sse with RD_STATS
structure.

Change-Id: I67429cff3112b32e14a8ffe5c38f50dcf4d79c64
diff --git a/av1/encoder/rd.h b/av1/encoder/rd.h
index 67add28..de8e0b3 100644
--- a/av1/encoder/rd.h
+++ b/av1/encoder/rd.h
@@ -379,6 +379,17 @@
 #endif
 }
 
+static INLINE void av1_accumulate_rd_stats(RD_STATS *rd_stats, int64_t dist,
+                                           int rate, int skip, int64_t sse,
+                                           int zero_rate) {
+  assert(rd_stats->rate != INT_MAX && rate != INT_MAX);
+  rd_stats->rate += rate;
+  if (!rd_stats->zero_rate) rd_stats->zero_rate = zero_rate;
+  rd_stats->dist += dist;
+  rd_stats->skip &= skip;
+  rd_stats->sse += sse;
+}
+
 static INLINE int64_t av1_calculate_rd_cost(int mult, int rate, int64_t dist) {
   assert(mult >= 0);
   if (rate >= 0) {