sim: Add a get_config_as_dict to the NullSimObject class.

Change-Id: I1ba6f6b196b7dfa790d1baaa23640bb3ed73f450
Reviewed-on: https://gem5-review.googlesource.com/4847
Maintainer: Gabe Black <gabeblack@google.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

src/python/m5/params.py

@@ -1721,6 +1721,9 @@ class NullSimObject(object):
         return
         yield None
 
+    def get_config_as_dict(self):
+        return {}
+
     def __str__(self):
         return self._name