arm: zynq: Sync up licenses with mainline kernel

Use different location for SPDX line. Also update dates for new mainline
DTS files.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/arch/arm/dts/zynq-zybo.dts b/arch/arm/dts/zynq-zybo.dts
index 52ec5a4..3844822 100644
--- a/arch/arm/dts/zynq-zybo.dts
+++ b/arch/arm/dts/zynq-zybo.dts
@@ -1,10 +1,7 @@
+// SPDX-License-Identifier: GPL-2.0+
 /*
- * Digilent ZYBO board DTS
- *
  *  Copyright (C) 2011 - 2015 Xilinx
  *  Copyright (C) 2012 National Instruments Corp.
- *
- * SPDX-License-Identifier:	GPL-2.0+
  */
 /dts-v1/;
 #include "zynq-7000.dtsi"