As the per-CPU initialization can fail, we need to deal with this
situation in cpufreq_remove_dev as the sysdev core doesn't (yet) do
this for us. The solution: add a "struct cpufreq_policy
*cpufreq_cpu_data[NR_CPUS]" array, which has a NULL pointer for each
CPU not managed by cpufreq (yet) and a pointer to the per-CPU data
for each CPU managed by cpufreq. It is locked by cpufreq_driver_lock.