No need to recalculate iv_length

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/src/psa_exercise_key.c b/tests/src/psa_exercise_key.c
index 3d2dfc6..415f885 100644
--- a/tests/src/psa_exercise_key.c
+++ b/tests/src/psa_exercise_key.c
@@ -181,7 +181,7 @@
     if( usage & PSA_KEY_USAGE_ENCRYPT )
     {
         PSA_ASSERT( psa_cipher_encrypt_setup( &operation, key, alg ) );
-        if( PSA_CIPHER_IV_LENGTH( key_type, alg ) != 0 )
+        if( iv_length != 0 )
         {
             PSA_ASSERT( psa_cipher_generate_iv( &operation,
                                                 iv, sizeof( iv ),