cpufreq: teach cpuinfo_{min,max}_freq as available frequencies
cpufreq: teach cpuinfo_{min,max}_freq as available frequencies

Summary:
The intel_pstate scaling driver exposes the `scaling_cur_freq` since
kernel 3.17 [*], it would be fine that the min and max frequencies
are known even without the `scaling_available_frequencie`.

This commit teaches to use the cpuinfo_{min,max}_freq as fallback in
case the `scaling_available_frequencies` is not available within
intel pstate.

[*] https://lkml.org/lkml/2014/11/11/1060

Signed-off-by: Takeshi Banse <takebi@laafc.net>

Subscribers: cedric

Differential Revision: https://phab.enlightenment.org/D1686

rvandegrift/e,tasn/enlightenment,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment,FlorentRevest/Enlightenment,tizenorg/platform.upstream.enlightenment,tasn/enlightenment,FlorentRevest/Enlightenment,tasn/enlightenment,tizenorg/platform.upstream.enlightenment,rvandegrift/e,rvandegrift/e