Add support for rejected inference responses

Change-Id: I62e13df69c712ed4cf70766429b4cb13fc9c9dcb
diff --git a/kernel/ethosu_core_interface.h b/kernel/ethosu_core_interface.h
index 5a6e55d..76fe35e 100644
--- a/kernel/ethosu_core_interface.h
+++ b/kernel/ethosu_core_interface.h
@@ -95,7 +95,9 @@
  */
 enum ethosu_core_status {
 	ETHOSU_CORE_STATUS_OK,
-	ETHOSU_CORE_STATUS_ERROR
+	ETHOSU_CORE_STATUS_ERROR,
+	ETHOSU_CORE_STATUS_RUNNING,
+	ETHOSU_CORE_STATUS_REJECTED,
 };
 
 /**