Add options setting number of tile groups or MTU.

Default MTU size is 0, which implies a fixed number
of tile groups. MTU matching overrides fixed tile
group. MTU matching will succeed unless a single
tile is bigger than the MTU.

--mtu-size is in bytes, and includes headers but
not transport/wrapper overheads

Change-Id: I2b70bd41b175b54273b02d836f2a84011f617a7c
diff --git a/av1/encoder/encodemv.c b/av1/encoder/encodemv.c
index 8a6ad18..e8ed909 100644
--- a/av1/encoder/encodemv.c
+++ b/av1/encoder/encodemv.c
@@ -142,9 +142,9 @@
                       aom_prob upd_p) {
   (void)upd_p;
 #if CONFIG_TILE_GROUPS
-  // Just use the maximum number of tile groups to avoid passing in the actual
+  // Just use the default maximum number of tile groups to avoid passing in the actual
   // number
-  av1_cond_prob_diff_update(w, cur_p, ct, MAX_NUM_TG);
+  av1_cond_prob_diff_update(w, cur_p, ct, DEFAULT_MAX_NUM_TG);
 #else
   av1_cond_prob_diff_update(w, cur_p, ct, 1);
 #endif