MISRA fix: Use boolean essential type

Change the return type of "arm_io_is_toc_valid()" and
"plat_arm_bl1_fwu_needed()" to bool, to match function behavior.

Change-Id: I503fba211219a241cb263149ef36ca14e3362a1c
Signed-off-by: Louis Mayencourt <louis.mayencourt@arm.com>
diff --git a/plat/arm/common/arm_io_storage.c b/plat/arm/common/arm_io_storage.c
index fc1eb49..60d19b2 100644
--- a/plat/arm/common/arm_io_storage.c
+++ b/plat/arm/common/arm_io_storage.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -357,12 +357,8 @@
  * See if a Firmware Image Package is available,
  * by checking if TOC is valid or not.
  */
-int arm_io_is_toc_valid(void)
+bool arm_io_is_toc_valid(void)
 {
-	int result;
-
-	result = io_dev_init(fip_dev_handle, (uintptr_t)FIP_IMAGE_ID);
-
-	return (result == 0);
+	return (io_dev_init(fip_dev_handle, (uintptr_t)FIP_IMAGE_ID) == 0);
 }