arm: dts: dm8x: Update devicetree header comments to sync with v6.3-rc6

Signed-off-by: Andrew Davis <afd@ti.com>
diff --git a/arch/arm/dts/dm816x.dtsi b/arch/arm/dts/dm816x.dtsi
index fe58faf..ae2d938 100644
--- a/arch/arm/dts/dm816x.dtsi
+++ b/arch/arm/dts/dm816x.dtsi
@@ -1,8 +1,4 @@
-/*
- * This file is licensed under the terms of the GNU General Public License
- * version 2.  This program is licensed "as is" without any warranty of any
- * kind, whether express or implied.
- */
+// SPDX-License-Identifier: GPL-2.0-only
 
 #include <dt-bindings/gpio/gpio.h>
 #include <dt-bindings/pinctrl/omap.h>