Allow compound mode when order hint isn't available

BUG=aomedia:1570

Change-Id: Ibd0c5cf2ae8b408ff2d4c791ef06c72c1a9ebfad
diff --git a/av1/decoder/decodeframe.c b/av1/decoder/decodeframe.c
index 9c429f2..59de549 100644
--- a/av1/decoder/decodeframe.c
+++ b/av1/decoder/decodeframe.c
@@ -89,10 +89,10 @@
 
 static REFERENCE_MODE read_frame_reference_mode(
     const AV1_COMMON *cm, struct aom_read_bit_buffer *rb) {
-  if (av1_is_compound_reference_allowed(cm)) {
-    return aom_rb_read_bit(rb) ? REFERENCE_MODE_SELECT : SINGLE_REFERENCE;
-  } else {
+  if (frame_is_intra_only(cm)) {
     return SINGLE_REFERENCE;
+  } else {
+    return aom_rb_read_bit(rb) ? REFERENCE_MODE_SELECT : SINGLE_REFERENCE;
   }
 }