mem-ruby: Replace deprecated Stats namespace with statistics

Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Change-Id: I5633510c91ba35852a63965bbe508e8965744093
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/62311
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/mem/ruby/structures/MN_TBEStorage.hh

@@ -64,7 +64,7 @@ template <class RetryEntry>
 class MN_TBEStorage
 {
   public:
-    MN_TBEStorage(Stats::Group *parent,
+    MN_TBEStorage(statistics::Group *parent,
                   std::initializer_list<TBEStorage *> _partitions)
       : m_stats(parent),
         partitions(_partitions)