crypto: fix transposed arguments in cipher error message

When reporting an incorrect key length for a cipher, we
mixed up the actual vs expected arguments.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
diff --git a/crypto/cipher.c b/crypto/cipher.c
index a24677c..7c33348 100644
--- a/crypto/cipher.c
+++ b/crypto/cipher.c
@@ -89,7 +89,7 @@
 
     if (alg_key_len[alg] != nkey) {
         error_setg(errp, "Cipher key length %zu should be %zu",
-                   alg_key_len[alg], nkey);
+                   nkey, alg_key_len[alg]);
         return false;
     }
     return true;