Add list_config generation

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/programs/test/query_config.h b/programs/test/query_config.h
index 23009c4..bcc348e 100644
--- a/programs/test/query_config.h
+++ b/programs/test/query_config.h
@@ -39,4 +39,12 @@
  */
 int query_config( const char *config );
 
+/** List all enabled configuration symbols
+ *
+ * \note            This function is defined in `programs/test/query_config.c`
+ *                  which is automatically generated by
+ *                  `scripts/generate_query_config.pl`.
+ */
+void list_config( void );
+
 #endif /* MBEDTLS_PROGRAMS_TEST_QUERY_CONFIG_H */