Avoid updating non-used transform

Since 32x32 transform use DCT only, we can avoid update other
types of transform

Change-Id: I51dd8ec71975187d249d7e25130e994a48cac5c1

av1/common/scan.h

@@ -93,6 +93,7 @@ static INLINE const SCAN_ORDER *get_default_scan(TX_SIZE tx_size,
 static INLINE int do_adapt_scan(TX_SIZE tx_size, TX_TYPE tx_type) {
   (void)tx_size;
 #if CONFIG_EXT_TX
+  if (tx_size == TX_32X32 && tx_type != DCT_DCT) return 0;
   return tx_type < IDTX;
 #else
   (void)tx_type;