Fix enc/dec mismatch bewteen mfmv and obu

BUG=aomedia:1123

Change-Id: I3886bd74cf3ee266eee13020c8821aff5b59e11d
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index d9e0990..dc3a174 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -4228,7 +4228,7 @@
     write_frame_interp_filter(cm->interp_filter, wb);
 #if CONFIG_TEMPMV_SIGNALING
     if (frame_might_use_prev_frame_mvs(cm)) {
-      aom_wb_write_bit(wb, cm->use_prev_frame_mvs);
+      aom_wb_write_bit(wb, cm->use_ref_frame_mvs);
     }
 #endif
   } else if (cm->frame_type == S_FRAME) {
@@ -4288,7 +4288,7 @@
     write_frame_interp_filter(cm->interp_filter, wb);
 #if CONFIG_TEMPMV_SIGNALING
     if (frame_might_use_prev_frame_mvs(cm)) {
-      aom_wb_write_bit(wb, cm->use_prev_frame_mvs);
+      aom_wb_write_bit(wb, cm->use_ref_frame_mvs);
     }
 #endif
   }