ARM: dts: exynos: Remove unnecessary address/size properties in dp-controller of Exynos5

The "dp-controller" node is not a bus and it does not have children with
reg/ranges properties so remove address-cells and size-cells properties.
This fixes warnings for all Exynos5 boards:

    arch/arm/boot/dts/exynos5250-arndale.dtb: Warning (avoid_unnecessary_addr_size):
        /soc/dp-controller@145b0000: unnecessary #address-cells/#size-cells without "ranges" or child "reg" property

Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>