Added @return to lambda javadoc

Change-Id: I1ec2414851595567fec444252ff9f374cc31240e
diff --git a/core/api/src/main/java/org/onosproject/net/Lambda.java b/core/api/src/main/java/org/onosproject/net/Lambda.java
index d0995be..47d0d5f 100644
--- a/core/api/src/main/java/org/onosproject/net/Lambda.java
+++ b/core/api/src/main/java/org/onosproject/net/Lambda.java
@@ -36,6 +36,7 @@
      * @param channelSpacing    channel spacing
      * @param spacingMultiplier channel spacing multiplier
      * @param slotGranularity   slot width granularity
+     * @return new lambda with specified arguments
      */
     static Lambda ochSignal(GridType gridType, ChannelSpacing channelSpacing,
                             int spacingMultiplier, int slotGranularity) {