Always use above predictor in under 8x8 chroma obmc

Change-Id: Ic23c96b78112ef9fbd7adad69f63bdbe3a56ce23

av1/common/reconinter.c

@@ -1762,8 +1762,8 @@ int skip_u4x4_pred_in_obmc(BLOCK_SIZE bsize, const struct macroblockd_plane *pd,
     case BLOCK_8X4:
     case BLOCK_4X8: return 1; break;
 #else
-    case BLOCK_4X4: return dir == 1; break;
-    case BLOCK_8X4: return dir == 0; break;
+    case BLOCK_4X4:
+    case BLOCK_8X4:
     case BLOCK_4X8: return dir == 1; break;
 #endif
     default: return 0;

av1/encoder/rdopt.c

@@ -9830,7 +9830,8 @@ void av1_rd_pick_inter_mode_sb(const AV1_COMP *cpi, TileDataEnc *tile_data,
 
 #if CONFIG_MOTION_VAR
   av1_count_overlappable_neighbors(cm, xd, mi_row, mi_col);
-  if (check_num_overlappable_neighbors(mbmi)) {
+  if (check_num_overlappable_neighbors(mbmi) &&
+      is_motion_variation_allowed_bsize(bsize)) {
     av1_build_prediction_by_above_preds(cm, xd, mi_row, mi_col,
                                         args.above_pred_buf, dst_width1,
                                         dst_height1, args.above_pred_stride);