Fix config flags among var-tx/ext-tx/rect-tx

BUG=aomedia:396

Change-Id: I1b7f6dddb06eac9e341518a95a0d71465e613e9e
diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index 587134f..3c63639 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -456,13 +456,9 @@
   FRAME_CONTEXT *ec_ctx = cm->fc;
 #endif
 // For sub8x8 blocks the tx_size symbol does not need to be sent
-#if CONFIG_CB4X4 && (CONFIG_VAR_TX || CONFIG_RECT_TX)
-#if CONFIG_RECT_TX
+#if CONFIG_CB4X4 && (CONFIG_VAR_TX || CONFIG_EXT_TX) && CONFIG_RECT_TX
   if (bsize > BLOCK_4X4) {
 #else
-  if (bsize >= BLOCK_8X8 || (bsize > BLOCK_4X4 && is_inter_block(mbmi))) {
-#endif  // CONFIG_RECT_TX
-#else
   if (bsize >= BLOCK_8X8) {
 #endif
     const TX_SIZE tx_size = mbmi->tx_size;