ARM: dts: Add exynos5420 peach-pit board support

Adds the google peach-pit board dts file which uses
exynos5420 SoC.

Signed-off-by: Arun Kumar K <arun.kk@samsung.com>
Signed-off-by: Doug Anderson <dianders@chromium.org>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>