ARM: S3C2410: move s3c2410_baseclk_add to clock.h

plat-samsung/clock.h currently keeps all the SoC specific clock
declarations. As we want to get rid of s3c2410.h altogether, move
the s3c2410_baseclk_add there too.

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