arm64: zynqmp: Sync up license with mainline kernel

Mainline Linux kernel has adopted SPDX header license in a different
format then was used before. This patch is syncing it up.

Also update years in License text and remove Nathalie's email because it
is no longer valid.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/dts/zynqmp.dtsi b/arch/arm/dts/zynqmp.dtsi
index e71399f..ad4bbbf 100644
--- a/arch/arm/dts/zynqmp.dtsi
+++ b/arch/arm/dts/zynqmp.dtsi
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0+
 /*
  * dts file for Xilinx ZynqMP
  *
@@ -5,7 +6,10 @@
  *
  * Michal Simek <michal.simek@xilinx.com>
  *
- * SPDX-License-Identifier:	GPL-2.0+
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
  */
 
 / {