learning_gem5: Adds the simple MemObject code

Adding more code from Learning gem5 Part II

See http://learning.gem5.org/book/part2/memoryobject.html

Change-Id: Iaa9480c5cdbe4090364f02e81dc1d0a0ddac392a
Signed-off-by: Jason Lowe-Power <jason@lowepower.com>
Reviewed-on: https://gem5-review.googlesource.com/5022
Reviewed-by: Nikos Nikoleris <nikos.nikoleris@arm.com>

src/learning_gem5/part2/SConscript

@@ -31,9 +31,12 @@ Import('*')
 
 SimObject('SimpleObject.py')
 SimObject('HelloObject.py')
+SimObject('SimpleMemobj.py')
 
 Source('simple_object.cc')
 Source('hello_object.cc')
 Source('goodbye_object.cc')
+Source('simple_memobj.cc')
 
 DebugFlag('HelloExample', "For Learning gem5 Part 2. Simple example debug flag")
+DebugFlag('SimpleMemobj', "For Learning gem5 Part 2.")