trusty: Include file with GIC definitions

The GIC definitions used in this file have to be provided by the platform
but platform_def.h wasn't included.

Change-Id: I858cdf7e60c50577c8e798d64ec2cbc4f067f33b
Signed-off-by: Antonio Nino Diaz <antonio.ninodiaz@arm.com>

services/spd/trusty/generic-arm64-smcall.c

 /*
- * Copyright (c) 2016-2018, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2016-2019, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -8,6 +8,7 @@
 
 #include <common/debug.h>
 #include <common/runtime_svc.h>
+#include <platform_def.h>
 
 #include "generic-arm64-smcall.h"