cpufreq: exynos: Use dev_err/info function instead of pr_err/info

This patch uses dev_err/info function to show accurate log message
with device name instead of pr_err/info function.

Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>