Unify to use ARRAY_SIZE in TF-M codes

ARRAY_SIZE(foo) is preferred over sizeof(foo)/sizeof(foo[0]).

Signed-off-by: Xinyu Zhang <xinyu.zhang@arm.com>
Change-Id: I6d95ceece2edc6267491923e282e28710b68ab8d
diff --git a/interface/src/tfm_initial_attestation_func_api.c b/interface/src/tfm_initial_attestation_func_api.c
index 5efe904..48dbbe1 100644
--- a/interface/src/tfm_initial_attestation_func_api.c
+++ b/interface/src/tfm_initial_attestation_func_api.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2020, Arm Limited. All rights reserved.
+ * Copyright (c) 2018-2021, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
@@ -11,8 +11,6 @@
 #include "psa/client.h"
 #include "psa/crypto_types.h"
 
-#define IOVEC_LEN(x) (sizeof(x)/sizeof(x[0]))
-
 psa_status_t
 psa_initial_attest_get_token(const uint8_t *auth_challenge,
                              size_t         challenge_size,