atomic: Adjust style a little bit
x86_64: Extract "Thermal and Power management Feature"

This feature will be used to detect whether LAPIC timer could be enabled
for deep C-states.
cputimer/intr: Restart only if the intr cputimer is changed
x86_64: Mark LAPIC timer as powersaving capable intr cputimer

If CPUID(0x6) has ARAT, then LAPIC timer will not stop in deep C-state.

Thank alexh@ for the necessary information.