ARM: EXYNOS: add support device tree enabled board file for EXYNOS5

This patch adds a new EXYNOS5 compatible device tree enabled board
When using this, a corresponding device tree blob which describes the
board's properties should be supplied at boot time to the kernel.

Cc: Thomas Abraham <thomas.abraham@linaro.org>
Cc: Grant Likely <grant.likely@secretlab.ca>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>