mem-ruby: Add a missing override.

Change-Id: I7651ca0f4658ddd49cfd13d9d5f7e430f416f41f
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/30254
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/system/VIPERCoalescer.hh

@@ -62,7 +62,7 @@ class VIPERCoalescer : public GPUCoalescer
     void issueRequest(CoalescedRequest* crequest) override;
     void wbCallback(Addr address);
     void invCallback(Addr address);
-    RequestStatus makeRequest(PacketPtr pkt);
+    RequestStatus makeRequest(PacketPtr pkt) override;
   private:
     void invL1();
     void wbL1();