Refactor the SF fast_inter_tx_type_search

The speed features fast_inter_tx_type_search and
default_inter_tx_type_prob_thresh have been combined
into  fast_inter_tx_type_prob_thresh

Change-Id: I8ae92a02ab67914f6c8744e604dc96e3edaf235d
diff --git a/av1/encoder/block.h b/av1/encoder/block.h
index 3ecc3fb..ebc388a 100644
--- a/av1/encoder/block.h
+++ b/av1/encoder/block.h
@@ -431,11 +431,7 @@
    * features.
    */
   int use_default_intra_tx_type;
-  /*! \brief Whether to limit the inter txfm search type to the default txfm.
-   *
-   * \copydetails use_default_intra_tx_type
-   */
-  int use_default_inter_tx_type;
+
   /*! Probability threshold used for conditionally forcing tx type*/
   int default_inter_tx_type_prob_thresh;