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/microsemi_olt/microsemi_olt.py b/voltha/adapters/microsemi_olt/microsemi_olt.py
index 152f8e3..addfd34 100644
--- a/voltha/adapters/microsemi_olt/microsemi_olt.py
+++ b/voltha/adapters/microsemi_olt/microsemi_olt.py
@@ -114,6 +114,9 @@
     def reenable_device(self, device):
         raise NotImplementedError()
 
+    def update_pm_config(self, device, pm_configs):
+        raise NotImplementedError()
+
     def reboot_device(self, device):
         raise NotImplementedError()