cpufreq: intel_pstate: Select schedutil as the default governor

Modify cpufreq Kconfig to select schedutil as the default governor
if the intel_pstate driver has been selected and SMP support is
enabled (because schedutil depends on SMP).

Also select schedutil as well as the performance governor from the
intel_pstate Kconfig section to ensure the equivalence of the passive
and active mode governor configuration options.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>