Upon resuming, first CPUfreq hardware support needs to be re-enabled in certain cases
(call to cpufreq_driver->resume()).
 
Then, two different paths may need to be taken:
a) frequency during suspend equals frequency during resume ==> everything is fine,
 
b) frequency differ ==> either we can't handle it, then panic (see flag
   CPUFREQ_PANIC_RESUME_OUTOFSYNC). Or we can handle it, then notify all