Add cdfs and mask buffers for mrc-tx

These are not currently being used for anything so there is
no impact on performance.

Change-Id: Ida4e0afcc10bee665f8daa379314cd18b3a4ea28
diff --git a/av1/common/blockd.h b/av1/common/blockd.h
index f66004a..57bf41a 100644
--- a/av1/common/blockd.h
+++ b/av1/common/blockd.h
@@ -776,6 +776,10 @@
   DECLARE_ALIGNED(16, uint8_t, seg_mask[2 * MAX_SB_SQUARE]);
 #endif  // CONFIG_EXT_INTER && CONFIG_COMPOUND_SEGMENT
 
+#if CONFIG_MRC_TX
+  uint8_t *mrc_mask;
+#endif  // CONFIG_MRC_TX
+
 #if CONFIG_CFL
   CFL_CTX *cfl;
 #endif