AV1 RT: Limit previous VBP threshold adjustment to HD

Change-Id: Id910d232dd987b79624a01fb03c7457828bd8141
diff --git a/av1/encoder/var_based_part.c b/av1/encoder/var_based_part.c
index ec664d9..5c61321 100644
--- a/av1/encoder/var_based_part.c
+++ b/av1/encoder/var_based_part.c
@@ -444,7 +444,7 @@
       else
         weight =
             1.0 - (current_qindex - QINDEX_LARGE_BLOCK_THR + win) / (2 * win);
-      if (cm->width * cm->height > 640 * 360) {
+      if (cm->width * cm->height > 640 * 480) {
         for (int i = 0; i < 4; i++) {
           thresholds[i] <<= 1;
         }