Cover intra tx size count in rect-tx

Account for intra tx size case when coding block is in skip mode.

Change-Id: I030bc05d890c4a7c8d4628a7f9bdebaba6083a03

av1/encoder/encodeframe.c

@@ -6147,7 +6147,7 @@ static void encode_superblock(const AV1_COMP *const cpi, ThreadData *td,
 
 #if CONFIG_VAR_TX
       mbmi->min_tx_size = get_min_tx_size(intra_tx_size);
-      if (intra_tx_size != max_txsize_lookup[bsize]) ++x->txb_split_count;
+      if (intra_tx_size != max_txsize_rect_lookup[bsize]) ++x->txb_split_count;
 #endif
     }