wrap TestHarness latency pipe in module

src/main/scala/rocketchip/TestHarness.scala

@@ -176,10 +176,22 @@ class JTAGVPI(implicit val p: Parameters) extends BlackBox {
   }
 }
 
-object LatencyPipe {
+class LatencyPipe[T <: Data](typ: T, latency: Int) extends Module {
+  val io = new Bundle {
+    val in = Decoupled(typ).flip
+    val out = Decoupled(typ)
+  }
+
   def doN[T](n: Int, func: T => T, in: T): T =
     (0 until n).foldLeft(in)((last, _) => func(last))
 
-  def apply[T <: Data](in: DecoupledIO[T], latency: Int): DecoupledIO[T] =
+  io.out <> doN(latency, (last: DecoupledIO[T]) => Queue(last, 1, pipe=true), io.in)
-    doN(latency, (last: DecoupledIO[T]) => Queue(last, 1, pipe=true), in)
+}
+
+object LatencyPipe {
+  def apply[T <: Data](in: DecoupledIO[T], latency: Int): DecoupledIO[T] = {
+    val pipe = Module(new LatencyPipe(in.bits, latency))
+    pipe.io.in <> in
+    pipe.io.out
+  }
 }