intel-pstate: Don't change scaling_governor if P-State isn't active
On systems without HWP support, or when the Intel P-State driver runs in "passive" mode, the CPU is effectively controlled by cpufreq governors.
Only modify the cpufreq scaling_governor if the Intel P-State driver is in active mode.
See https://www.kernel.org/doc/html/v5.17/admin-guide/pm/intel_pstate.html#operation-modes
Closes: #91 (closed)