ARM: dts: add pinctrl support to EXYNOS5420

Add the required pin configuration support to EXYNOS5420
using pinctrl interface.

Signed-off-by: Leela Krishna Amudala <l.krishna@samsung.com>
Reviewed-by: Doug Anderson <dianders@chromium.org>
Acked-by: Tomasz Figa <t.figa@samsung.com>
Tested-by : Sunil Joshi <joshi@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>