Properly handle the tile load size writing

Properly handle the tile load size writing operations in ext-tile
when large-scale-tile is on and off. This fixes an enc/dec mismatch
issue when both ext-tile and obu are turned on.

BUG=aomedia:1179

Change-Id: I460e0cd55ba5d0bf5b75b5a5f6866c8774693207

av1/encoder/bitstream.c

diff --git a/av1/encoder/bitstream.c b/av1/encoder/bitstream.c
index b27b906..3fe2717 100644
--- a/av1/encoder/bitstream.c
+++ b/av1/encoder/bitstream.c
@@ -4217,7 +4217,7 @@
 #if CONFIG_EXT_TILE
   *saved_wb = *wb;
   // Write tile size magnitudes
-  if (cm->tile_rows * cm->tile_cols > 1) {
+  if (cm->tile_rows * cm->tile_cols > 1 && cm->large_scale_tile) {
     // Note that the last item in the uncompressed header is the data
     // describing tile configuration.
     // Number of bytes in tile column size - 1