psa: driver wrapper: cipher: Fix unused variable warning

Signed-off-by: Ronald Cron <ronald.cron@arm.com>
diff --git a/library/psa_crypto_driver_wrappers.c b/library/psa_crypto_driver_wrappers.c
index 20f1abd..8d86478 100644
--- a/library/psa_crypto_driver_wrappers.c
+++ b/library/psa_crypto_driver_wrappers.c
@@ -949,6 +949,8 @@
             (void)key_buffer;
             (void)key_buffer_size;
             (void)alg;
+            (void)iv;
+            (void)iv_length;
             (void)input;
             (void)input_length;
             (void)output;