Add rsa+kw testing support to simulator

Allows simulating images signed with RSA-2048 and encrypted with
AES-128-KW.

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/sim/src/tlv.rs b/sim/src/tlv.rs
index 6931d0b..afc34aa 100644
--- a/sim/src/tlv.rs
+++ b/sim/src/tlv.rs
@@ -107,6 +107,16 @@
         }
     }
 
+    #[allow(dead_code)]
+    pub fn new_rsa_kw() -> TlvGen {
+        TlvGen {
+            flags: TlvFlags::ENCRYPTED as u32,
+            kinds: vec![TlvKinds::SHA256, TlvKinds::RSA2048, TlvKinds::ENCKW128],
+            size: 4 + 32 + 4 + 32 + 4 + 256 + 4 + 24,
+            payload: vec![],
+        }
+    }
+
     /// Retrieve the header flags for this configuration.  This can be called at any time.
     pub fn get_flags(&self) -> u32 {
         self.flags