mem-garnet: Enable bridge rescheduling for DVFS

The Bridge SimObject, which hosts the CDC and SerDes functionality,
could be woken up out-of-order when changing frequencies in DVFS.
This change ensures there is no packet drop during the transition
times.

Change-Id: I40240dcb3e957217abd2d7ad22cc4f78809f7b49
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/44287
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/mem/ruby/network/garnet/NetworkBridge.cc

@@ -257,7 +257,10 @@ NetworkBridge::wakeup()
         t_flit = link_srcQueue->getTopFlit();
         DPRINTF(RubyNetwork, "Recieved flit %s\n", *t_flit);
         flitisizeAndSend(t_flit);
-        return;
     }
-    assert(!link_srcQueue->getSize());
+
+    // Reschedule in case there is a waiting flit.
+    if (!link_srcQueue->isEmpty()) {
+        scheduleEvent(Cycles(1));
+    }
 }