fix a warning with windows build

Change-Id: I100a29e3846d437c30853d68902d2704dbc8d39d

av1/common/tile_common.h

diff --git a/av1/common/tile_common.h b/av1/common/tile_common.h
index 617dda2..e34ee7c 100644
--- a/av1/common/tile_common.h
+++ b/av1/common/tile_common.h
@@ -38,7 +38,7 @@
 void av1_tile_set_row(TileInfo *tile, const struct AV1Common *cm, int row);
 void av1_tile_set_col(TileInfo *tile, const struct AV1Common *cm, int col);
 #if CONFIG_DEPENDENT_HORZTILES && CONFIG_TILE_GROUPS
-void av1_tile_set_tg_boundary(TileInfo *tile, const struct AV1Common *cm,
+void av1_tile_set_tg_boundary(TileInfo *tile, const struct AV1Common *const cm,
                               int row, int col);
 #endif
 void av1_get_tile_n_bits(int mi_cols, int *min_log2_tile_cols,