Move the tx pruning flags into MACROBLOCK

So they can be generated at prediction block, and then easily
accessed by transform block.

Change-Id: I376042e8d57e00586d3cf90e237544e705b77e8b
diff --git a/av1/encoder/block.h b/av1/encoder/block.h
index 0b334cf..4e6b8ee 100644
--- a/av1/encoder/block.h
+++ b/av1/encoder/block.h
@@ -365,6 +365,8 @@
   int comp_idx_cost[COMP_INDEX_CONTEXTS][2];
   int comp_group_idx_cost[COMP_GROUP_IDX_CONTEXTS][2];
 #endif  // CONFIG_JNT_COMP
+  // Bit flags for pruning tx type search, tx split, etc.
+  int tx_search_prune[EXT_TX_SET_TYPES];
 };
 
 static INLINE int is_rect_tx_allowed_bsize(BLOCK_SIZE bsize) {