Fix Bug libc/28945

- apply fix from Tom de Vries <vries@gcc.gnu.org>
  to have calloc zero out storage for nvptx calloc function

newlib/libc/machine/nvptx/calloc.c

@@ -22,5 +22,5 @@ calloc (size_t size, size_t len)
   void *p = malloc (size * len);
   if (!p)
     return p;
-  return memset (p, 0, len);
+  return memset (p, 0, size * len);
 }