ARM: dts: exynos: Fix port nodes names for Exynos5250 Snow board

Commit 5c9cbade ("ARM: dts: exynos: Fix DTC unit name warnings in
Exynos5250") fixed all the DTC warnings about mismatchs between unit
names and reg properties in Exynos5250 boards DTS.

But unfortunately it also added a regression on the Exynos5250 Snow
Chromebook when changing the port node names since the OF graph logic
expects the port nodes to be always named 'port'.

The Documentation/devicetree/bindings/graph.txt binding document says
that when there is more than one port, '#address-cells', '#size-cells'
and 'reg' properties should be used to number the port nodes.

Fixes: 5c9cbade ("ARM: dts: exynos: Fix DTC unit name warnings in Exynos5250")
Reported-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Tested-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>

arch/arm/boot/dts/exynos5250-snow-common.dtsi

@@ -242,7 +242,7 @@ &dp {
 	hpd-gpios = <&gpx0 7 GPIO_ACTIVE_HIGH>;
 
 	ports {
-		port0 {
+		port {
 			dp_out: endpoint {
 				remote-endpoint = <&bridge_in>;
 			};
@@ -485,13 +485,20 @@ ptn3460: lvds-bridge@20 {
 		edid-emulation = <5>;
 
 		ports {
-			port0 {
+			#address-cells = <1>;
+			#size-cells = <0>;
+
+			port@0 {
+				reg = <0>;
+
 				bridge_out: endpoint {
 					remote-endpoint = <&panel_in>;
 				};
 			};
 
-			port1 {
+			port@1 {
+				reg = <1>;
+
 				bridge_in: endpoint {
 					remote-endpoint = <&dp_out>;
 				};