oops, close the handle after use as a good citizen

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@14367 a1c6a512-1295-4272-9138-f99709370657

tools/mkinfo.pl

@@ -42,6 +42,8 @@ sub mapscan {
             $start = $1;
         }
     }
+    close(M);
+
     # return number of bytes
     return hex($end) - hex($start);
 }