ARM: multi_v7_defconfig: Enable NTC Thermistors support

The Exynos5420 Peach Pit and Exynos5800 Peach Pi Chromebooks have
IIO based ADC thermistors. Enable module support for its driver
and also for the needed Exynos ADC driver.

Signed-off-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Kukjin Kim <kgene@kernel.org>