Add device tree based discovery support for Samsung's rtc controller.

Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: NThomas Abraham <thomas.abraham@linaro.org>
Acked-by: NGrant Likely <grant.likely@secretlab.ca>
Signed-off-by: NKukjin Kim <kgene.kim@samsung.com>