cpufreq: drop owner assignment from platform_drivers

This platform_driver does not need to set an owner, it will be
populated by the driver core.

Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>