[ARM] S3C24XX: Split DCLK/CLKOUT definitions out of clock.c

Only certain boards need these clocks, and they are not
available on some CPUs (such as the S3C24A0) so remove
them from arch/arm/plat-s3c24xx/clock.c and into their
own file with appropriate Kconfig entries.

Signed-off-by: Ben Dooks <ben-linux@fluff.org>