cpufreq: intel_pstate: Fix active mode setting from command line

If intel_pstate starts in the passive mode by default (that happens
when the processor in the system doesn't support HWP), passing
intel_pstate=active in the kernel command line doesn't work, so
fix that.

Fixes: 33aa46f252c7 ("cpufreq: intel_pstate: Use passive mode by default without HWP")
Reported-by: Doug Smythies <dsmythies@telus.net>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Acked-by: Doug Smythies <dsmythies@telus.net>