Change assert(MAX_MB_PLANE == 3) to static_assert

Change-Id: I193f968146639b269ca0424cec0d1e9c0cc5c5bf

av1/common/thread_common.c

diff --git a/av1/common/thread_common.c b/av1/common/thread_common.c
index 0ff6238..dee45b4 100644
--- a/av1/common/thread_common.c
+++ b/av1/common/thread_common.c
@@ -9,6 +9,8 @@
  * PATENTS file, you can obtain it at www.aomedia.org/license/patent.
  */
 
+#include <assert.h>
+
 #include "aom/aom_image.h"
 #include "config/aom_config.h"
 #include "config/aom_scale_rtcd.h"
@@ -938,7 +940,7 @@
   }
 
   int i;
-  assert(MAX_MB_PLANE == 3);
+  static_assert(MAX_MB_PLANE == 3, "");
 
   if (!lr_sync->sync_range || num_rows_lr > lr_sync->rows ||
       num_workers > lr_sync->num_workers || num_planes > lr_sync->num_planes) {