cpufreq: intel_pstate: Use CPUFREQ_POLICY_UNKNOWN

epp_policy uses the same values as cpufreq_policy.policy and resets
to CPUFREQ_POLICY_UNKNOWN during offlining. Be consistent about
it and initialize to CPUFREQ_POLICY_UNKNOWN instead of 0, too.

No functional change intended.

Signed-off-by: Christian Loehle <christian.loehle@arm.com>
Link: https://patch.msgid.link/20241211122605.3048503-3-christian.loehle@arm.com


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