ARM: dts: Add support for EXYNOS4X12 SoCs

This patch adds device tree sources for EXYNOS4X12 SoC series
(currently EXYNOS4212 and EXYNOS4412) and enables mach-exynos4-dt
to support these SoCs.

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