cpufreq: Drop unused dev argument from two functions

The dev argument of cpufreq_add_policy_cpu() and
cpufreq_add_dev_interface() is not used by any of them,
so drop it.

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