dt-bindings: add binding for clock-controller of s3c2443 and following

Starting with the s3c2443 the s3c24xx series got a new clock tree
compared to the previous s3c24xx socs. This binding describes the
clock controller found in the s3c2443, s3c2416 and s3c2450 socs.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Tomasz Figa <t.figa@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>