ath79: teltonika-rut230: fix typo in "green:signal-strength4" LED

It's missing a hyphen present in every other LED from the set. Set it to
"green:signal-strength-4".

Signed-off-by: Lech Perczak <lech.perczak@gmail.com>
Link: https://github.com/openwrt/openwrt/pull/17503


Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>

target/linux/ath79/dts/ar9331_teltonika_rut230-v1.dts

@@ -68,7 +68,7 @@
 		};
 
 		signal-strength-4 {
-			label = "green:signal-strength4";
+			label = "green:signal-strength-4";
 			gpios = <&gpio 27 GPIO_ACTIVE_HIGH>;
 		};