[mlr] configure MLR.req response status (#5350)

include/openthread/backbone_router_ftd.h

@@ -193,6 +193,18 @@ void otBackboneRouterConfigNextDuaRegistrationResponse(otInstance *
                                                        const otIp6InterfaceIdentifier *aMlIid,
                                                        uint8_t                         aStatus);
 
+/**
+ * This method configures response status for next Multicast Listener Registration.
+ *
+ * Note: available only when `OPENTHREAD_CONFIG_REFERENCE_DEVICE_ENABLE` is enabled.
+ *       Only used for test and certification.
+ *
+ * @param[in] aInstance  A pointer to an OpenThread instance.
+ * @param[in] aStatus    The status to respond.
+ *
+ */
+void otBackboneRouterConfigNextMulticastListenerRegistrationResponse(otInstance *aInstance, uint8_t aStatus);
+
 /**
  * Represents the Multicast Listener events.
  *