ARM: dts: Use labels for overriding nodes in exynos4412-odroid

Usage of labels instead of full paths reduces possible mistakes when
overriding nodes.
Signed-off-by: Krzysztof Kozlowski <k.kozlowski.k@gmail.com>

For thermal zones:
Acked-by: Eduardo Valentin <edubezval@gmail.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>

arch/arm/boot/dts/exynos4412-odroidx.dts

@@ -38,14 +38,6 @@ led2 {
 		};
 	};
 
-	serial@13820000 {
-		status = "okay";
-	};
-
-	serial@13830000 {
-		status = "okay";
-	};
-
 	gpio_keys {
 		pinctrl-0 = <&gpio_power_key &gpio_home_key>;
 
@@ -83,3 +75,11 @@ gpio_home_key: home_key {
 		samsung,pin-pud = <0>;
 	};
 };
+
+&serial_2 {
+	status = "okay";
+};
+
+&serial_3 {
+	status = "okay";
+};