mem-cache: print when hitting on a prefetched line

Only print it on the first it on a prefetched line
(as the prefetched flag is removed after the first hit)
This is useful when debugging prefetchers.

Change-Id: Id67cc957c7366a244bedad93824a3c4fdf2055b5
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/47601
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Daniel Carvalho <odanrc@yahoo.com.br>

src/mem/cache/base.cc

@@ -380,6 +380,8 @@ BaseCache::recvTimingReq(PacketPtr pkt)
         ppHit->notify(pkt);
 
         if (prefetcher && blk && blk->wasPrefetched()) {
+            DPRINTF(Cache, "Hit on prefetch for addr %#x (%s)\n",
+                    pkt->getAddr(), pkt->isSecure() ? "s" : "ns");
             blk->clearPrefetched();
         }