Platform: Update the include statements

Change the absolute including into relative path including
for platform sources.

Change-Id: I594577eae7689ea8ac6cb557d5b0b5a048ee9b4d
Signed-off-by: Mingyang Sun <mingyang.sun@arm.com>
diff --git a/platform/ext/common/template/nv_counters.c b/platform/ext/common/template/nv_counters.c
index f2c230e..f1fb28c 100644
--- a/platform/ext/common/template/nv_counters.c
+++ b/platform/ext/common/template/nv_counters.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2018-2019, Arm Limited. All rights reserved.
+ * Copyright (c) 2018-2020, Arm Limited. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  *
@@ -20,7 +20,7 @@
  * for testing purposes.
  */
 
-#include "platform/include/tfm_plat_nv_counters.h"
+#include "tfm_plat_nv_counters.h"
 
 #include <limits.h>
 #include "Driver_Flash.h"