perfbias: Implement Intel performance-energy hint support

This hint is set on per-logical CPU. 0 delivers highest performance;
15 maximizes energy saving. It could be set through sysctl nodes
mach

perfbias: Implement Intel performance-energy hint support

This hint is set on per-logical CPU. 0 delivers highest performance;
15 maximizes energy saving. It could be set through sysctl nodes
machdep.perfbiasX (X is the CPU id).

It is linked into i386 and x86_64 GENERIC kernel.

* We may want to make powerd(8) to aware of these sysctls.

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