Copy device serial number to logical device in openolt

Change-Id: Ic5ff2b337526895d91990b3d29c77890468d8c4d
diff --git a/voltha/adapters/openolt/openolt_device.py b/voltha/adapters/openolt/openolt_device.py
index a6ec890..d1f6a2d 100644
--- a/voltha/adapters/openolt/openolt_device.py
+++ b/voltha/adapters/openolt/openolt_device.py
@@ -29,7 +29,7 @@
 from voltha.protos.openflow_13_pb2 import OFPPS_LIVE, OFPPF_FIBER, \
     OFPPS_LINK_DOWN, OFPPF_1GB_FD, OFPC_GROUP_STATS, OFPC_PORT_STATS, \
     OFPC_TABLE_STATS, OFPC_FLOW_STATS, ofp_switch_features, ofp_port, \
-    ofp_port_stats
+    ofp_port_stats, ofp_desc
 from voltha.protos.logical_device_pb2 import LogicalPort
 from voltha.core.logical_device_agent import mac_str_to_tuple
 from voltha.registry import registry
@@ -124,6 +124,9 @@
                         | OFPC_PORT_STATS
                         | OFPC_GROUP_STATS
                     )
+                ),
+                desc=ofp_desc(
+                    serial_num=device.serial_number
                 )
             )
             ld_init = self.adapter_agent.create_logical_device(ld,