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>