EXYNOS5: Snow: Add a configuration file

This patch adds the configuration file for Snow Board and
defines the same in boards.cfg.

Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com>
Acked-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>