cpufreq: schedutil: Simplify sugov_fast_switch()

Drop a redundant local variable definition from sugov_fast_switch()
and rearrange the code in there to avoid the redundant logical
negation.

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