cpufreq: Drop unnecessary label from cpufreq_add_dev()

The leftover out_release_rwsem label in cpufreq_add_dev() is not
necessary any more and confusing, so drop it.

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