plat: xilinx: zynqmp: Move zynqmp_private.h to include directory

Move zynqmp_private.h to platform specific include directory.
Also, rename it to plat_private.h instead of having platform
name. So, it can be used to common source files which needs
platform specific data.

Signed-off-by: Tejas Patel <tejas.patel@xilinx.com>
Reviewed-by: Siva Durga Prasad Paladugu <siva.durga.paladugu@xilinx.com>
Signed-off-by: Jolly Shah <jollys@xilinx.com>
diff --git a/plat/xilinx/zynqmp/plat_startup.c b/plat/xilinx/zynqmp/plat_startup.c
index 03f0e3d..cd2c3ba 100644
--- a/plat/xilinx/zynqmp/plat_startup.c
+++ b/plat/xilinx/zynqmp/plat_startup.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2014-2016, ARM Limited and Contributors. All rights reserved.
+ * Copyright (c) 2014-2018, ARM Limited and Contributors. All rights reserved.
  *
  * SPDX-License-Identifier: BSD-3-Clause
  */
@@ -9,9 +9,9 @@
 #include <arch_helpers.h>
 #include <common/debug.h>
 #include <lib/mmio.h>
+#include <plat_private.h>
 
 #include "zynqmp_def.h"
-#include "zynqmp_private.h"
 
 /*
  * ATFHandoffParams