Added the interface and the stubbs to update the PM config for the
devices. Sample code for the simulated OLT and ponsim will be provided
in a subsequent update.  Also deleted some commented out lines that were no longer
relevant to clean up the code a bit.

Change-Id: I8c7ba9a957ae2b7ba8ec816410bfb9ba01527625
diff --git a/voltha/adapters/ponsim_onu/ponsim_onu.py b/voltha/adapters/ponsim_onu/ponsim_onu.py
index 36d0013..493145c 100644
--- a/voltha/adapters/ponsim_onu/ponsim_onu.py
+++ b/voltha/adapters/ponsim_onu/ponsim_onu.py
@@ -87,6 +87,9 @@
     def change_master_state(self, master):
         raise NotImplementedError()
 
+    def update_pm_config(self, device, pm_configs):
+        raise NotImplementedError()
+
     def adopt_device(self, device):
         self.devices_handlers[device.id] = PonSimOnuHandler(self, device.id)
         reactor.callLater(0, self.devices_handlers[device.id].activate, device)