Fix enc/dec mismatch in global motion

Resolve an enc/dec mismatch issue when global motion is turned on.

BUG=aomedia:424

Change-Id: Ifad02fab4412588527ec7e8b24ab9b8c6327e5ba

av1/common/blockd.h

@@ -1248,9 +1248,6 @@ static INLINE int is_nontrans_global_motion(const MACROBLOCKD *xd) {
     if (mbmi->mode != ZEROMV) return 0;
 #endif  // CONFIG_EXT_INTER
   } else {
-#if !GLOBAL_SUB8X8_USED
-    return 0;
-#endif  // !GLOBAL_SUB8X8_USED
 #if CONFIG_EXT_INTER
     if (mi->bmi[0].as_mode != ZEROMV || mi->bmi[1].as_mode != ZEROMV ||
         mi->bmi[2].as_mode != ZEROMV || mi->bmi[3].as_mode != ZEROMV ||
@@ -1264,6 +1261,11 @@ static INLINE int is_nontrans_global_motion(const MACROBLOCKD *xd) {
       return 0;
 #endif  // CONFIG_EXT_INTER
   }
+
+#if !GLOBAL_SUB8X8_USED
+  if (mbmi->sb_type < BLOCK_8X8) return 0;
+#endif
+
   // Now check if all global motion is non translational
   for (ref = 0; ref < 1 + has_second_ref(mbmi); ++ref) {
     if (xd->global_motion[mbmi->ref_frame[ref]].wmtype <= TRANSLATION) return 0;