ARM: dts: Enable on-board keys as wakeup source for exynos4210-origen

On board keys on Origen board can serve as wakeup sources,
hence they are marked accordingly in the device tree file.

Signed-off-by: Tushar Behera <tushar.behera@linaro.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>