AV1 RT: Include 64x64 blocks in merge check on speed 7

This gives 0.6% BDRate improvement and the speed impact is either
neutral or 2-3% improved (because of early exits?)

Change-Id: I4a08f5021814d9ca063baac5b7371de2db559ee6
diff --git a/av1/encoder/partition_search.c b/av1/encoder/partition_search.c
index 1cdd383..583e680 100644
--- a/av1/encoder/partition_search.c
+++ b/av1/encoder/partition_search.c
@@ -2098,7 +2098,7 @@
       }
       if (cpi->sf.rt_sf.nonrd_check_partition_merge_mode &&
           av1_is_leaf_split_partition(cm, mi_row, mi_col, bsize) &&
-          !frame_is_intra_only(cm) && bsize <= BLOCK_32X32) {
+          !frame_is_intra_only(cm) && bsize <= BLOCK_64X64) {
         RD_SEARCH_MACROBLOCK_CONTEXT x_ctx;
         RD_STATS split_rdc, none_rdc;
         av1_invalid_rd_stats(&split_rdc);