ACPI: Avoid wiping out pr->performance during preregistering

When cpufreq driver call acpi_processor_preregister_performance() , function
will clean up pr->performance even if there is possibly already registered
other cpufreq driver. The patch fix this potential problem. It also remove
double checks in P domain basic validity code and move these checks to function
where _PSD data is captured.

Signed-off-by: Stanislaw Gruszka <sgruszka@redhat.com>
Signed-off-by: Len Brown <len.brown@intel.com>