ARM: dts: exynos: Add sysreg phandle to ADC node

Instead of using the ADC_PHY register base address, use sysreg phandle
in ADC node to control ADC_PHY configuration register.

This patch adds syscon node for Exynos3250, Exynos4x12, Exynos5250,
and Exynos5420, Exynos5800.

Signed-off-by: Naveen Krishna Chatradhi <ch.naveen@samsung.com>
To: linux-samsung-soc@vger.kernel.org
Acked-by: Kukjin Kim <kgene.kim@samsung.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>