Fix a compiler warning with = { 0 } assignment

BUG=aomedia:2455

Change-Id: If6c1fd566026471a8f8e661a36f27d4054d25d3b
diff --git a/av1/encoder/temporal_filter.c b/av1/encoder/temporal_filter.c
index f3f554f..8941760 100644
--- a/av1/encoder/temporal_filter.c
+++ b/av1/encoder/temporal_filter.c
@@ -1032,7 +1032,8 @@
 
   // Make a temporary mbmi for temporal filtering
   MB_MODE_INFO **backup_mi_grid = mbd->mi;
-  MB_MODE_INFO mbmi = { 0 };
+  MB_MODE_INFO mbmi;
+  memset(&mbmi, 0, sizeof(mbmi));
   MB_MODE_INFO *mbmi_ptr = &mbmi;
   mbd->mi = &mbmi_ptr;
 
diff --git a/av1/encoder/tpl_model.c b/av1/encoder/tpl_model.c
index 9f9eb81..f2378ed 100644
--- a/av1/encoder/tpl_model.c
+++ b/av1/encoder/tpl_model.c
@@ -499,7 +499,8 @@
 
   // Make a temporary mbmi for tpl model
   MB_MODE_INFO **backup_mi_grid = xd->mi;
-  MB_MODE_INFO mbmi = { 0 };
+  MB_MODE_INFO mbmi;
+  memset(&mbmi, 0, sizeof(mbmi));
   MB_MODE_INFO *mbmi_ptr = &mbmi;
   xd->mi = &mbmi_ptr;