ruby: Fix memory leak in AbstractController

Recent changes to memory access queuing allocate requests for packets sent to
memory controllers, but did not free the requests. Delete them to avoid leaks.

src/mem/ruby/slicc_interface/AbstractController.cc

@@ -328,6 +328,7 @@ AbstractController::recvTimingResp(PacketPtr pkt)
     }
 
     getMemoryQueue()->enqueue(msg, clockEdge(), cyclesToTicks(Cycles(1)));
+    delete pkt->req;
     delete pkt;
 }