mem-cache: Make checking function const in FALRU

The checking function should not be able to modify either
the head and tail pointers nor should it modify its class.

Change-Id: I2ad495f0c8c6b778d48512143e94b4c9a353f22e
Signed-off-by: Daniel R. Carvalho <odanrc@yahoo.com.br>
Reviewed-on: https://gem5-review.googlesource.com/c/13209
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Maintainer: Nikos Nikoleris <nikos.nikoleris@arm.com>

src/mem/cache/tags/fa_lru.cc

@@ -283,10 +283,10 @@ FALRUParams::create()
 }
 
 void
-FALRU::CacheTracking::check(FALRUBlk *head, FALRUBlk *tail)
+FALRU::CacheTracking::check(const FALRUBlk *head, const FALRUBlk *tail) const
 {
 #ifdef FALRU_DEBUG
-    FALRUBlk* blk = head;
+    const FALRUBlk* blk = head;
     unsigned curr_size = 0;
     unsigned tracked_cache_size = minTrackedSize;
     CachesMask in_caches_mask = inAllCachesMask;

src/mem/cache/tags/fa_lru.hh

@@ -335,7 +335,7 @@ class FALRU : public BaseTags
          * @param head the MRU block of the actual cache
          * @param head the LRU block of the actual cache
          */
-        void check(FALRUBlk *head, FALRUBlk *tail);
+        void check(const FALRUBlk *head, const FALRUBlk *tail) const;
 
         /**
          * Register the stats for this object.