arm64: dts: rockchip: rename LED label for NanoPi R4S

However "sys" is not a valid function, and it is always on.
Let's keep existing functions.

Fixes: db792e9a ("rockchip: rk3399: Add support for FriendlyARM NanoPi R4S")
Suggested-by: Pavel Machek <pavel@ucw.cz>
Signed-off-by: Tianling Shen <cnsztl@gmail.com>
Acked-by: Pavel Machek <pavel@ucw.cz>
Link: https://lore.kernel.org/r/20210426114652.29542-1-cnsztl@gmail.comSigned-off-by: Heiko Stuebner <heiko@sntech.de>

arch/arm64/boot/dts/rockchip/rk3399-nanopi-r4s.dts

@@ -33,7 +33,7 @@ lan_led: led-lan {
 
 		sys_led: led-sys {
 			gpios = <&gpio0 RK_PB5 GPIO_ACTIVE_HIGH>;
-			label = "red:sys";
+			label = "red:power";
 			default-state = "on";
 		};