Ruby: Add support for functional accesses

This patch rpovides functional access support in Ruby. Currently only
the M5Port of RubyPort supports functional accesses. The support for
functional through the PioPort will be added as a separate patch.

src/mem/ruby/system/SConscript

@@ -33,9 +33,8 @@ Import('*')
 if not env['RUBY']:
     Return()
 
-SimObject('Cache.py')
+SimObject('AbstractMemory.py')
 SimObject('Sequencer.py')
-SimObject('DirectoryMemory.py')
 SimObject('MemoryControl.py')
 SimObject('WireBuffer.py')
 SimObject('RubySystem.py')