ruby: Move Rubys cache class from Cache.py to RubyCache.py

This patch serves to avoid name clashes with the classic cache. For
some reason having two 'SimObject' files with the same name creates
problems.

--HG--
rename : src/mem/ruby/structures/Cache.py => src/mem/ruby/structures/RubyCache.py

configs/ruby/MI_example.py

@@ -37,7 +37,7 @@ from Ruby import send_evicts
 #
 # Declare caches used by the protocol
 #
-class Cache(RubyCache): pass
+class L1Cache(RubyCache): pass
 
 def define_options(parser):
     return
@@ -70,9 +70,9 @@ def create_system(options, full_system, system, dma_ports, ruby_system):
         # Only one cache exists for this protocol, so by default use the L1D
         # config parameters.
         #
-        cache = Cache(size = options.l1d_size,
-                      assoc = options.l1d_assoc,
-                      start_index_bit = block_size_bits)
+        cache = L1Cache(size = options.l1d_size,
+                        assoc = options.l1d_assoc,
+                        start_index_bit = block_size_bits)
 
         #
         # Only one unified L1 cache exists.  Can cache instructions and data.