cpufreq: Rearrange __cpufreq_driver_target()

Drop a pointless label at a return statement from
__cpufreq_driver_target() and rearrange that function
to reduce the indentation level.

No intentional functional changes.

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