feat(mbedtls): update mbedtls to version 3.6.4

Signed-off-by: Lauren Wehrmeister <lauren.wehrmeister@arm.com>
Change-Id: Icdd5e6d12ee8c85980ce74ae0ec9cfb64d9ead6c
diff --git a/utils.sh b/utils.sh
index c4af89f..ed9877b 100644
--- a/utils.sh
+++ b/utils.sh
@@ -624,7 +624,7 @@
 
 linaro_2001_release="${linaro_2001_release:-$tfa_downloads/linaro/20.01}"
 linaro_release="${linaro_release:-$linaro_2001_release}"
-mbedtls_version="${mbedtls_version:-3.6.3}"
+mbedtls_version="${mbedtls_version:-3.6.4}"
 
 # mbedTLS archive public hosting available at github.com
 mbedtls_archive="${mbedtls_archive:-https://github.com/Mbed-TLS/mbedtls/archive/mbedtls-${mbedtls_version}.tar.gz}"