Add n8_h/w to macroblockd

This will simplify the block size update in many places.

Change-Id: I255093692315d81340900baea6ccee0c02b9abd4

av1/common/blockd.h

@@ -185,6 +185,8 @@ typedef struct macroblockd {
   int mb_to_top_edge;
   int mb_to_bottom_edge;
 
+  uint8_t n8_w, n8_h;
+
   FRAME_CONTEXT *fc;
 
   /* pointers to reference frames */

av1/common/onyxc_int.h

@@ -459,6 +459,9 @@ static INLINE void set_mi_row_col(MACROBLOCKD *xd, const TileInfo *const tile,
     xd->left_mi = NULL;
     xd->left_mbmi = NULL;
   }
+
+  xd->n8_h = bh;
+  xd->n8_w = bw;
 }
 
 static INLINE const aom_prob *get_y_mode_probs(const AV1_COMMON *cm,