mem-cache: Delete squashed HWPrefetches

Request and Packet for squashed HWPrefetches were not deleted

Change-Id: I9b66bb01b8ed6a5ddfaaa8739a68165dc4a7006c
Signed-off-by: Pau Cabre <pau.cabre@metempsy.com>
Reviewed-on: https://gem5-review.googlesource.com/4340
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

src/mem/cache/cache.cc

@@ -2419,6 +2419,11 @@ Cache::sendMSHRQueuePacket(MSHR* mshr)
                 // mshr when all had previously been utilized
                 clearBlocked(Blocked_NoMSHRs);
             }
+
+            // given that no response is expected, delete Request and Packet
+            delete tgt_pkt->req;
+            delete tgt_pkt;
+
             return false;
         }
     }