Improve SingleInstructionLimiterPlugin to also include fetch stages

src/main/scala/vexriscv/plugin/SingleInstructionLimiterPlugin.scala

@@ -9,7 +9,9 @@ class SingleInstructionLimiterPlugin() extends Plugin[VexRiscv] {
   override def build(pipeline: VexRiscv): Unit = {
     import pipeline._
     import pipeline.config._
-
-    decode.arbitration.haltByOther.setWhen(List(decode,execute,memory,writeBack).map(_.arbitration.isValid).orR)
+    val fetcher = pipeline.service(classOf[IBusFetcher])
+    when(fetcher.incoming() || List(decode,execute,memory,writeBack).map(_.arbitration.isValid).orR) {
+      fetcher.haltIt()
+    }
   }
 }