ARM: dts: exynos: Add HDMI CEC device to Exynos5 SoC family

Exynos5250 and Exynos542x SoCs have the same CEC hardware module as
Exynos4 SoC series, so enable support for it using the same compatible
string.

Tested on Odroid XU3 (Exynos5422) and Google Snow (Exynos5250) boards.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>