ARM: S5PV310: Add support CPUFREQ

This patch adds support CPUFREQ driver for S5PV310 and S5PC210. This can
support DVFS(Dynamic Voltage and Frequency Scaling). The voltage scaling
depends on existence of regulator.

Sigend-off-by: Sunyoung Kang <sy0816.kang@samsung.com>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>