ARM: dts: use key code macros on Origen and Arndale boards

Key code macros improve readability on exnos4210-origen,
exynos4412-origen and exynos5250-arndale boards.

Signed-off-by: Sachin Kamat <sachin.kamat@linaro.org>
[kgene.kim@samsung.com: squashed similar two patches]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>