feat(mbedtls): upgrade to version v2.28.8

Signed-off-by: Yann Gautier <yann.gautier@st.com>
Change-Id: I05b73733135d0d3704ed484cf8eb4aed84631a48
diff --git a/utils.sh b/utils.sh
index 57cf9d9..6626de6 100644
--- a/utils.sh
+++ b/utils.sh
@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 #
-# Copyright (c) 2019-2023, Arm Limited. All rights reserved.
+# Copyright (c) 2019-2024, Arm Limited. All rights reserved.
 #
 # SPDX-License-Identifier: BSD-3-Clause
 #
@@ -642,7 +642,7 @@
 
 linaro_2001_release="${linaro_2001_release:-$tfa_downloads/linaro/20.01}"
 linaro_release="${linaro_release:-$linaro_2001_release}"
-mbedtls_version="${mbedtls_version:-2.28.5}"
+mbedtls_version="${mbedtls_version:-2.28.8}"
 
 # mbedTLS archive public hosting available at github.com
 mbedtls_archive="${mbedtls_archive:-https://github.com/Mbed-TLS/mbedtls/archive/refs/tags/v${mbedtls_version}.tar.gz}"