mem-cache: Ensure all fields of the CacheBlk class are initialized.

The constructor only initialized two fields, data and _tickInserted. The
print() method at least accesses the coherence status bits, which
valgrind determined were being accessed without being initialized.

This change adds a default initializer to all fields to prevent any
value from flapping around uninitialized.

Change-Id: Ie4c839504d49f9a131d8e3c3e8be02ff22f453a6
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52404
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br>
Maintainer: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/mem/cache/cache_blk.hh

@@ -100,13 +100,13 @@ class CacheBlk : public TaggedEntry
      * data stored here should be kept consistant with the actual data
      * referenced by this block.
      */
-    uint8_t *data;
+    uint8_t *data = nullptr;
 
     /**
      * Which curTick() will this block be accessible. Its value is only
      * meaningful if the block is valid.
      */
-    Tick whenReady;
+    Tick whenReady = 0;
 
   protected:
     /**
@@ -152,7 +152,7 @@ class CacheBlk : public TaggedEntry
     std::list<Lock> lockList;
 
   public:
-    CacheBlk() : TaggedEntry(), data(nullptr), _tickInserted(0)
+    CacheBlk()
     {
         invalidate();
     }
@@ -474,22 +474,22 @@ class CacheBlk : public TaggedEntry
 
   private:
     /** Task Id associated with this block */
-    uint32_t _taskId;
+    uint32_t _taskId = 0;
 
     /** holds the source requestor ID for this block. */
-    int _srcRequestorId;
+    int _srcRequestorId = 0;
 
     /** Number of references to this block since it was brought in. */
-    unsigned _refCount;
+    unsigned _refCount = 0;
 
     /**
      * Tick on which the block was inserted in the cache. Its value is only
      * meaningful if the block is valid.
      */
-    Tick _tickInserted;
+    Tick _tickInserted = 0;
 
     /** Whether this block is an unaccessed hardware prefetch. */
-    bool _prefetched;
+    bool _prefetched = 0;
 };
 
 /**