Drop support for VIA Padlock

Signed-off-by: Thomas Daubney <thomas.daubney@arm.com>
diff --git a/SECURITY.md b/SECURITY.md
index 7ed72de..9506eb9 100644
--- a/SECURITY.md
+++ b/SECURITY.md
@@ -128,7 +128,7 @@
 
 - Turn on hardware acceleration for AES. This is supported only on selected
   architectures and currently only available for AES. See configuration options
-  `MBEDTLS_AESCE_C`, `MBEDTLS_AESNI_C` and `MBEDTLS_PADLOCK_C` for details.
+  `MBEDTLS_AESCE_C`, `MBEDTLS_AESNI_C` for details.
 - Add a secure alternative implementation (typically hardware acceleration) for
   the vulnerable cipher. See the [Alternative Implementations
 Guide](docs/architecture/alternative-implementations.md) for more information.