build: Be explicit that we want integers when dividing for python3 compat.

Signed-off-by: Johannes Krampf <johannes.krampf@googlemail.com>
diff --git a/scripts/checkrom.py b/scripts/checkrom.py
index e724844..30c9db2 100755
--- a/scripts/checkrom.py
+++ b/scripts/checkrom.py
@@ -86,7 +86,7 @@
     print("Total size: %d  Fixed: %d  Free: %d (used %.1f%% of %dKiB rom)" % (
         datasize, runtimesize, finalsize - datasize
         , (datasize / float(finalsize)) * 100.0
-        , finalsize / 1024))
+        , int(finalsize / 1024)))
 
     # Write final file
     f = open(outfile, 'wb')