TLS: Add tls_connection_peer_serial_num()

This can be used to fetch the serial number of the peer certificate in
the EAP server. For now, this is implemented only with OpenSSL.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>

src/crypto/tls_internal.c

@@ -177,6 +177,14 @@ int tls_connection_established(void *tls_ctx, struct tls_connection *conn)
 }
 
 
+char * tls_connection_peer_serial_num(void *tls_ctx,
+				      struct tls_connection *conn)
+{
+	/* TODO */
+	return NULL;
+}
+
+
 int tls_connection_shutdown(void *tls_ctx, struct tls_connection *conn)
 {
 #ifdef CONFIG_TLS_INTERNAL_CLIENT