arm64: dts: rockchip: add phandle to timer0 on rk3368

While the kernel doesn't care s0 much right now, bootloaders like
u-boot need to refine the node on their side, so to make life easier
for everyone add the timer0 phandle for timer0.
Signed-off-by: Heiko Stuebner <heiko.stuebner@theobroma-systems.com>
Link: https://lore.kernel.org/r/20210209103408.2302218-1-heiko@sntech.deSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3368.dtsi

@@ -667,7 +667,7 @@ wdt: watchdog@ff800000 {
 		status = "disabled";
 	};
 
-	timer@ff810000 {
+	timer0: timer@ff810000 {
 		compatible = "rockchip,rk3368-timer", "rockchip,rk3288-timer";
 		reg = <0x0 0xff810000 0x0 0x20>;
 		interrupts = <GIC_SPI 66 IRQ_TYPE_LEVEL_HIGH>;