add enum value to string helpers

Only add helpers for enum in `ssl.h`.

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/library/ssl_tls13_server.c b/library/ssl_tls13_server.c
index 3018ecb..e9c74ca 100644
--- a/library/ssl_tls13_server.c
+++ b/library/ssl_tls13_server.c
@@ -26,6 +26,7 @@
 #include "mbedtls/debug.h"
 
 #include "ssl_misc.h"
+#include "ssl_debug_helpers_generated.h"
 
 int mbedtls_ssl_tls13_handshake_server_step( mbedtls_ssl_context *ssl )
 {