mem-cache: Allow prefetchers to override setCache.

This lets them hook setCache, perhaps to set up additional state based
on the set cache.

Change-Id: Ic3b34fa43d052c71e8ef733a57fe47c70899cd27
Reviewed-on: https://gem5-review.googlesource.com/8701
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Gabe Black <gabeblack@google.com>

src/mem/cache/prefetch/base.hh

@@ -125,7 +125,7 @@ class BasePrefetcher : public ClockedObject
 
     virtual ~BasePrefetcher() {}
 
-    void setCache(BaseCache *_cache);
+    virtual void setCache(BaseCache *_cache);
 
     /**
      * Notify prefetcher of cache access (may be any access or just