asyncqueue: Fix typo in the Async Queue (#381)

* asyncqueue: Fix typo in the Async Queue that would cause the sync depth to be one less than expected.

* asyncqueue: Typo in the typo fix

src/main/scala/util/AsyncQueue.scala

@@ -21,7 +21,7 @@ object AsyncGrayCounter {
         sink.io.d := source.io.q
         sink.io.en := Bool(true)
       }
-    syncv(0).io.d
+    syncv.head.io.q
   }
 }