tls13: add dummy state machine handler

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
index 725b156..0abcb75 100644
--- a/include/mbedtls/ssl.h
+++ b/include/mbedtls/ssl.h
@@ -623,6 +623,7 @@
     MBEDTLS_SSL_SERVER_HELLO_VERIFY_REQUEST_SENT,
 #if defined(MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL)
     MBEDTLS_SSL_ENCRYPTED_EXTENSIONS,
+    MBEDTLS_SSL_CLIENT_CERTIFICATE_VERIFY,
 #endif /* MBEDTLS_SSL_PROTO_TLS1_3_EXPERIMENTAL */
 }
 mbedtls_ssl_states;