Fix unused param warnings in auth_xxcrypt_ext()

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
diff --git a/library/cipher.c b/library/cipher.c
index ee365a1..457f8f6 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -1552,6 +1552,9 @@
         if( iv_len != 0 || tag_len != 0 || ad_len != 0 )
             return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
 
+        (void) iv;
+        (void) ad;
+
         return( mbedtls_nist_kw_wrap( ctx->cipher_ctx, mode, input, ilen,
                                       output, olen, output_len ) );
     }
@@ -1605,6 +1608,9 @@
         if( iv_len != 0 || tag_len != 0 || ad_len != 0 )
             return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
 
+        (void) iv;
+        (void) ad;
+
         return( mbedtls_nist_kw_unwrap( ctx->cipher_ctx, mode, input, ilen,
                                         output, olen, output_len ) );
     }