Fix decoding failure in cb4x4 and var-tx mode

Fix the bit-stream decoding failure introduced lately in cb4x4
and var-tx mode.

Change-Id: Id671b5ec98b32d65e4fb45812ee8d1b7037fd6ec

av1/decoder/decodemv.c

@@ -401,7 +401,7 @@ static TX_SIZE read_tx_size(AV1_COMMON *cm, MACROBLOCKD *xd, int is_inter,
   const BLOCK_SIZE bsize = xd->mi[0]->mbmi.sb_type;
   if (xd->lossless[xd->mi[0]->mbmi.segment_id]) return TX_4X4;
 #if CONFIG_CB4X4 && CONFIG_VAR_TX
-  if (bsize > BLOCK_4X4) {
+  if ((bsize > BLOCK_4X4 && is_inter) || bsize >= BLOCK_8X8) {
 #else
   if (bsize >= BLOCK_8X8) {
 #endif  // CONFIG_CB4X4 && CONFIG_VAR_TX