ARM: dts: Add ADC's dt data to read raw data for exynos4x12

This patch add ADC(Analog to Digital Converter)'s dt data to get raw data
with IIO subsystem. Usually, ADC is used to check temperature, jack type
and so on.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Reviewed-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>