cpufreq: s5pv210: Don't flood kernel log after cpufreq change

This commit replaces printk with pr_debug, so we don't flood kernel log.

Signed-off-by: Paweł Chmiel <pawel.mikolaj.chmiel@gmail.com>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>