caps: add ECIES-P256

Signed-off-by: Fabio Utzig <utzig@apache.org>
diff --git a/sim/src/caps.rs b/sim/src/caps.rs
index fa7c41e..35ab14f 100644
--- a/sim/src/caps.rs
+++ b/sim/src/caps.rs
@@ -14,6 +14,7 @@
     ValidatePrimarySlot  = (1 << 7),
     RSA3072              = (1 << 8),
     Ed25519              = (1 << 9),
+    EncEc256             = (1 << 10),
 }
 
 impl Caps {