[ARM] S3C64XX: Initial support for DVFS

This patch provides initial support for CPU frequency scaling on the
Samsung S3C ARM processors. Currently only S3C6410 processors are
supported, though addition of another data table with supported clock
rates should be sufficient to enable support for further CPUs.

Use the regulator framework to provide optional support for DVFS in
the S3C cpufreq driver. When a software controllable regulator is
configured the driver will use it to lower the supply voltage when
running at a lower frequency, giving improved power savings.

When regulator support is disabled or no regulator can be obtained
for VDDARM the driver will fall back to scaling only the frequency.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>