Move common/utils.go to device/utils.go.

The utility functions ConvB2S(), OnuToSn(), LoggerWithOnu() in common/utils.go strongly depend on ONU instance specification.
Then, I consider it should be in device package that contains ONU instance , not utils package.

Change-Id: I7fd2b21c5f7c51be8ec4a5c161da9c93e3a3f582
diff --git a/core/openolt_service.go b/core/openolt_service.go
index dc48577..489e185 100644
--- a/core/openolt_service.go
+++ b/core/openolt_service.go
@@ -20,7 +20,6 @@
 	"time"
 
 	"gerrit.opencord.org/voltha-bbsim/common/logger"
-	"gerrit.opencord.org/voltha-bbsim/common/utils"
 	"gerrit.opencord.org/voltha-bbsim/device"
 	openolt "gerrit.opencord.org/voltha-bbsim/protos"
 )
@@ -88,24 +87,24 @@
 		logger.Error("Failed to send ONUDiscInd [id: %d]: %v", onu.OnuID, err)
 		return err
 	}
-	utils.LoggerWithOnu(onu).Info("sendONUDiscInd Onuid")
+	device.LoggerWithOnu(onu).Info("sendONUDiscInd Onuid")
 	return nil
 }
 
 func sendOnuInd(stream openolt.Openolt_EnableIndicationServer, onu *device.Onu, delay int, operState string, adminState string) error {
 	time.Sleep(time.Duration(delay) * time.Millisecond)
 	data := &openolt.Indication_OnuInd{OnuInd: &openolt.OnuIndication{
-		IntfId:         onu.IntfID,
-		OnuId:          onu.OnuID,
-		OperState:      operState,
-		AdminState:     adminState,
-		SerialNumber:   onu.SerialNumber,
+		IntfId:       onu.IntfID,
+		OnuId:        onu.OnuID,
+		OperState:    operState,
+		AdminState:   adminState,
+		SerialNumber: onu.SerialNumber,
 	}}
 	if err := stream.Send(&openolt.Indication{Data: data}); err != nil {
 		logger.Error("Failed to send ONUInd [id: %d]: %v", onu.OnuID, err)
 		return err
 	}
-	utils.LoggerWithOnu(onu).Info("sendONUInd Onuid")
+	device.LoggerWithOnu(onu).Info("sendONUInd Onuid")
 	return nil
 }