cpufreq: Use CONFIG_CPU_FREQ_DEFAULT_* to set initial policy for setpolicy drivers

When configuring a default governor (via CONFIG_CPU_FREQ_DEFAULT_*) with the
intel_pstate driver, the desired default policy is not properly set. For
example, setting 'CONFIG_CPU_FREQ_DEFAULT_GOV_PERFORMANCE' ends up with the
'powersave' policy being set.

Fix by configuring the correct default policy, if either 'powersave' or
'performance' are requested. Otherwise, fallback to what the driver originally
set via its 'init' routine.

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