fix(mtd): correct types in messages

Some messages don't use the correct types, update them.
This avoids warning when -Wformat-signedness is enabled.

Change-Id: Ie5384a7d139c48a623e1617c93d15fecc8a36061
Signed-off-by: Yann Gautier <yann.gautier@st.com>
diff --git a/drivers/io/io_mtd.c b/drivers/io/io_mtd.c
index ba8cecd..5d86592 100644
--- a/drivers/io/io_mtd.c
+++ b/drivers/io/io_mtd.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2019-2021, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2019-2022, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -8,13 +8,13 @@
 #include <errno.h>
 #include <string.h>
 
-#include <platform_def.h>
-
 #include <common/debug.h>
 #include <drivers/io/io_driver.h>
 #include <drivers/io/io_mtd.h>
 #include <lib/utils.h>
 
+#include <platform_def.h>
+
 typedef struct {
 	io_mtd_dev_spec_t	*dev_spec;
 	uintptr_t		base;
@@ -214,7 +214,7 @@
 	ops = &cur->dev_spec->ops;
 	assert(ops->read != NULL);
 
-	VERBOSE("Read at %llx into %lx, length %zi\n",
+	VERBOSE("Read at %llx into %lx, length %zu\n",
 		cur->base + cur->pos, buffer, length);
 	if ((cur->base + cur->pos + length) > cur->dev_spec->device_size) {
 		return -EINVAL;