ARM: EXYNOS: Add Exynos4 device tree enabled board file

Add a new EXYNOS4 compatible device tree enabled board file. Boards
based on the EXYNOS4 family of SoC's can use this as the machine/board
file. When using this machine fike, a corresponding device tree blob
which describes the board's properties should be supplied at boot time
to the kernel.

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