arm64: dts: renesas: gray-hawk-single: Mark SWDT as reserved

This watchdog can't be used with Linux because the firmware needs it on
R-Car V4M Gray Hawk Single boards.  Sadly, it doesn't mark the node as
reserved, so this is added manually here.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20251006082520.10570-20-wsa+renesas@sang-engineering.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
diff --git a/arch/arm64/boot/dts/renesas/gray-hawk-single.dtsi b/arch/arm64/boot/dts/renesas/gray-hawk-single.dtsi
index 2edb5cb..f5b3d88 100644
--- a/arch/arm64/boot/dts/renesas/gray-hawk-single.dtsi
+++ b/arch/arm64/boot/dts/renesas/gray-hawk-single.dtsi
@@ -801,6 +801,11 @@ &scif_clk2 {
 	clock-frequency = <24000000>;
 };
 
+/* Firmware should reserve it but sadly doesn't */
+&swdt {
+	status = "reserved";
+};
+
 &vin00 {
 	status = "okay";
 };