cpufreq: schedutil: Make it depend on CONFIG_SMP

Make the schedutil cpufreq governor depend on CONFIG_SMP, because
the scheduler-provided utilization numbers used by it are only
available with CONFIG_SMP set.

Fixes: 9bdcb44e (cpufreq: schedutil: New governor based on scheduler utilization data)
Reported-by: Steve Muckle <steve.muckle@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>