Add label attribute used to uniquely identify next-hop-group.

Author: Kishore Gummadidala

inc/sainexthopgroup.h

@@ -279,6 +279,15 @@ typedef enum _sai_next_hop_group_attr_t
      */
     SAI_NEXT_HOP_GROUP_ATTR_NEXT_HOP_MEMBER_COUNTER_LIST,
 
+    /**
+     * @brief Label attribute used to uniquely identify next-hop-group.
+     *
+     * @type char
+     * @flags CREATE_AND_SET
+     * @default ""
+     */
+    SAI_NEXT_HOP_GROUP_ATTR_LABEL,
+
     /**
      * @brief End of attributes
      */