ARM: dts: exynos: Add ADCs on 4412 and 5422 based odroid boards.

Odroid-X, -X2, -XU3 and -XU4 have SOC-ADC routed to an external connector.
Enable the ADC for use as iio-device.

Signed-off-by: Markus Reichl <m.reichl@fivetechno.de>
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>