Do memread stalling correctly.

src/main/scala/IDBarrier.scala

@@ -27,9 +27,11 @@ class IDBarrier extends MultiIOModule {
     new Bundle {
       val in = Input(new IDBarrierIO)
       val out = Output(new IDBarrierIO)
+      val stall = Output(Bool())
     })
 
   val delay = Reg(new IDBarrierIO)
   delay := io.in
   io.out := delay
+  io.stall := io.out.memRead
 }