Correct misleading variable name, mi_8x8

Change them to mi_4x4.

Change-Id: Ifb64db6c93ab59c3ed0b63945888a523732dbac7

av1/encoder/encodeframe.c

diff --git a/av1/encoder/encodeframe.c b/av1/encoder/encodeframe.c
index 2874c5c..503376d 100644
--- a/av1/encoder/encodeframe.c
+++ b/av1/encoder/encodeframe.c
@@ -4625,8 +4625,8 @@
   const int num_planes = av1_num_planes(cm);
   MACROBLOCK *const x = &td->mb;
   MACROBLOCKD *const xd = &x->e_mbd;
-  MB_MODE_INFO **mi_8x8 = xd->mi;
-  MB_MODE_INFO *mbmi = mi_8x8[0];
+  MB_MODE_INFO **mi_4x4 = xd->mi;
+  MB_MODE_INFO *mbmi = mi_4x4[0];
   const int seg_skip =
       segfeature_active(&cm->seg, mbmi->segment_id, SEG_LVL_SKIP);
   const int mis = cm->mi_stride;
@@ -4749,7 +4749,7 @@
       for (j = 0; j < mi_height; j++)
         for (i = 0; i < mi_width; i++)
           if (mi_col + i < cm->mi_cols && mi_row + j < cm->mi_rows)
-            mi_8x8[mis * j + i]->tx_size = intra_tx_size;
+            mi_4x4[mis * j + i]->tx_size = intra_tx_size;
 
       if (intra_tx_size != get_max_rect_tx_size(bsize)) ++x->txb_split_count;
     }

av1/encoder/encoder.c

diff --git a/av1/encoder/encoder.c b/av1/encoder/encoder.c
index eca1563d..78a5c9a 100644
--- a/av1/encoder/encoder.c
+++ b/av1/encoder/encoder.c
@@ -685,16 +685,16 @@
 
 static void update_reference_segmentation_map(AV1_COMP *cpi) {
   AV1_COMMON *const cm = &cpi->common;
-  MB_MODE_INFO **mi_8x8_ptr = cm->mi_grid_visible;
+  MB_MODE_INFO **mi_4x4_ptr = cm->mi_grid_visible;
   uint8_t *cache_ptr = cm->current_frame_seg_map;
   int row, col;
 
   for (row = 0; row < cm->mi_rows; row++) {
-    MB_MODE_INFO **mi_8x8 = mi_8x8_ptr;
+    MB_MODE_INFO **mi_4x4 = mi_4x4_ptr;
     uint8_t *cache = cache_ptr;
-    for (col = 0; col < cm->mi_cols; col++, mi_8x8++, cache++)
-      cache[0] = mi_8x8[0]->segment_id;
-    mi_8x8_ptr += cm->mi_stride;
+    for (col = 0; col < cm->mi_cols; col++, mi_4x4++, cache++)
+      cache[0] = mi_4x4[0]->segment_id;
+    mi_4x4_ptr += cm->mi_stride;
     cache_ptr += cm->mi_cols;
   }
 }