ARM: S3C: CPUFREQ: Move struct s3c_cpufreq_config to cpu-freq-core.h

Move the structure s3c_cpufreq_config from cpu-freq.h to the
less advertised cpu-freq-core.h as it is not needed by anything
outside the core drivers.

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