Fix disabling of speed feature for enc row-mt

Speed features for enc row-mt are now disabled only if
--row_mt=1 is passed as an encoding parameter and num of
threads > 1.

Change-Id: I53bf00af4b965a5361fa8f64d93cc1c4ac72b5e6
diff --git a/av1/encoder/speed_features.c b/av1/encoder/speed_features.c
index c14e8bd..c8865bb 100644
--- a/av1/encoder/speed_features.c
+++ b/av1/encoder/speed_features.c
@@ -575,7 +575,7 @@
 
   if (cpi->oxcf.using_dist_8x8) x->min_partition_size = BLOCK_8X8;
 #endif  // CONFIG_DIST_8X8
-  if (cpi->oxcf.row_mt == 1) {
+  if (cpi->oxcf.row_mt == 1 && (cpi->oxcf.max_threads > 1)) {
     sf->adaptive_rd_thresh = 0;
     sf->inter_mode_rd_model_estimation = 0;
   }