Sim: Add testcases for AES256 image encryption

Signed-off-by: Salome Thirot <salome.thirot@arm.com>
diff --git a/sim/src/caps.rs b/sim/src/caps.rs
index 1d9a612..4af8bd0 100644
--- a/sim/src/caps.rs
+++ b/sim/src/caps.rs
@@ -1,6 +1,6 @@
 // Copyright (c) 2017-2019 Linaro LTD
 // Copyright (c) 2019 JUUL Labs
-// Copyright (c) 2019 Arm Limited
+// Copyright (c) 2019-2021 Arm Limited
 //
 // SPDX-License-Identifier: Apache-2.0
 
@@ -25,6 +25,7 @@
     DowngradePrevention  = (1 << 12),
     EncX25519            = (1 << 13),
     Bootstrap            = (1 << 14),
+    Aes256               = (1 << 15),
 }
 
 impl Caps {