mem: Pass snoop retries through the CommMonitor

Allow the monitor to be placed after a snooping port, and do not fail
on snoop retries, but instead pass them on to the slave port.

src/mem/comm_monitor.cc

@@ -344,6 +344,12 @@ CommMonitor::recvTimingSnoopResp(PacketPtr pkt)
     return masterPort.sendTimingSnoopResp(pkt);
 }
 
+void
+CommMonitor::recvRetrySnoopResp()
+{
+    slavePort.sendRetrySnoopResp();
+}
+
 bool
 CommMonitor::isSnooping() const
 {

src/mem/comm_monitor.hh

@@ -167,6 +167,11 @@ class CommMonitor : public MemObject
             mon.recvReqRetry();
         }
 
+        void recvRetrySnoopResp()
+        {
+            mon.recvRetrySnoopResp();
+        }
+
       private:
 
         CommMonitor& mon;
@@ -248,6 +253,8 @@ class CommMonitor : public MemObject
 
     bool recvTimingSnoopResp(PacketPtr pkt);
 
+    void recvRetrySnoopResp();
+
     AddrRangeList getAddrRanges() const;
 
     bool isSnooping() const;