arm64: dts: renesas: gray-hawk-single: Enable watchdog timer

Enable the watchdog timer on the Gray Hawk Single board.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/cf6effafd9e0472a457eed9d84a834abc3e1c833.1706790320.git.geert+renesas@glider.be

arch/arm64/boot/dts/renesas/r8a779h0-gray-hawk-single.dts

@@ -47,6 +47,11 @@ &hscif0 {
 	status = "okay";
 };
 
+&rwdt {
+	timeout-sec = <60>;
+	status = "okay";
+};
+
 &scif_clk {
 	clock-frequency = <24000000>;
 };