Explain that the script is only for the future

Signed-off-by: David Horstmann <david.horstmann@arm.com>
diff --git a/scripts/code_style.py b/scripts/code_style.py
index 4aa9a40..f93df7b 100755
--- a/scripts/code_style.py
+++ b/scripts/code_style.py
@@ -1,5 +1,9 @@
 #!/usr/bin/env python3
 """Check or fix the code style by running Uncrustify.
+
+Note: The code style enforced by this script is not yet introduced to
+Mbed TLS. At present this script will only be used to prepare for a future
+change of code style.
 """
 # Copyright The Mbed TLS Contributors
 # SPDX-License-Identifier: Apache-2.0