mem: Add DRAMSys wrapper as a memory object

Add a DRAMSys wrapper to the gem5 memory source that
instantiates the DRAMSys simulator.
Another DRAMSys SimObject implements the AbstractMemory
interface and exposes the tlm target socket.

Change-Id: I8a95e729905e0924453043e5e7744df7a7ce4548
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/62912
Tested-by: kokoro <noreply+kokoro@google.com>
Maintainer: Bobby Bruce <bbruce@ucdavis.edu>
Reviewed-by: Bobby Bruce <bbruce@ucdavis.edu>

src/mem/SConscript

@@ -121,6 +121,10 @@ if env['HAVE_DRAMSIM3']:
     Source('dramsim3_wrapper.cc')
     Source('dramsim3.cc')
 
+if env['HAVE_DRAMSYS']:
+    SimObject('DRAMSys.py', sim_objects=['DRAMSys'])
+    Source('dramsys_wrapper.cc')
+
 SimObject('MemChecker.py', sim_objects=['MemChecker', 'MemCheckerMonitor'])
 Source('mem_checker.cc')
 Source('mem_checker_monitor.cc')