Coverity: remove unnecessary header file includes

This patch removes unnecessary header file includes
discovered by Coverity HFA option.

Change-Id: I2827c37c1c24866c87db0e206e681900545925d4
Signed-off-by: Zelalem <zelalem.aweke@arm.com>
diff --git a/plat/arm/css/common/css_pm.c b/plat/arm/css/common/css_pm.c
index 01c674f..af69c6f 100644
--- a/plat/arm/css/common/css_pm.c
+++ b/plat/arm/css/common/css_pm.c
@@ -1,11 +1,10 @@
 /*
- * Copyright (c) 2015-2019, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2015-2020, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
 
 #include <assert.h>
-#include <errno.h>
 
 #include <platform_def.h>
 
@@ -15,7 +14,6 @@
 #include <lib/cassert.h>
 #include <plat/arm/common/plat_arm.h>
 #include <plat/arm/css/common/css_pm.h>
-#include <plat/common/platform.h>
 
 /* Allow CSS platforms to override `plat_arm_psci_pm_ops` */
 #pragma weak plat_arm_psci_pm_ops