Fix L2 TLB response bug

Sometimes, it would inform the L1 TLB that the translation was for
a superpage, even though that's never the case.

src/main/scala/rocket/PTW.scala

@@ -261,6 +261,7 @@ class PTW(n: Int)(implicit edge: TLEdgeOut, p: Parameters) extends CoreModule()(
     resp_valid(r_req_dest) := true
     resp_ae := false
     r_pte := l2_pte
+    count := pgLevels-1
   }
 }