ARM: dts: exynos: Fix port nodes names for Exynos5420 Peach Pit board

Commit bea7eef6 ("ARM: dts: exynos: Fix DTC unit name warnings in
Peach Pit") fixed the DTC warnings about mismatches between unit names
and reg properties in the Exynos5420 Peach Pit DTS.

But unfortunately it also added a regression on the Peach Pit 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: bea7eef6 ("ARM: dts: exynos: Fix DTC unit name warnings in  Peach Pit")
Reported-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>