ACPI: Reevaluate whether the T-state is supported or not after cpu is online/offline

After one CPU is offlined, it is unnecessary to switch T-state for it.
So it will be better that the throttling is disabled after the cpu
is offline.
At the same time after one cpu is online, we should check whether
the T-state is supported and then set the corresponding T-state
flag.

Signed-off-by: Zhao Yakui <yakui.zhao@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>