cpufreq: sa11x0: let cpufreq core initialize struct policy fields

Many fields of struct policy are filled by cpufreq core when we call
cpufreq_table_validate_and_show() and so cpufreq driver doesn't need to set them
anymore.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>