frame_superres: Use calculate_scaled_size for scale check

Small change to calculate the encode size for scale checking using the
av1_calculate_scaled_size function used elsewhere instead of calculating
it in place. Done for constistency's sake.

Change-Id: I72626b729477e28e868cf9028ea4537267a12413

av1/encoder/ratectrl.c

diff --git a/av1/encoder/ratectrl.c b/av1/encoder/ratectrl.c
index d16f81d..b546fdf 100644
--- a/av1/encoder/ratectrl.c
+++ b/av1/encoder/ratectrl.c
@@ -1717,8 +1717,8 @@
   }
 
   // Make sure overall reduction is no more than 1/2 of the source size.
-  if (new_num * width / SCALE_DENOMINATOR * 2 < oxcf->width ||
-      new_num * height / SCALE_DENOMINATOR * 2 < oxcf->height)
+  av1_calculate_scaled_size(&width, &height, new_num);
+  if (width * 2 < oxcf->width || height * 2 < oxcf->height)
     new_num = SCALE_DENOMINATOR;
 
   return new_num;