If package-level control is present, we default to using it. Per-core
software control may be enabled by setting the machdep.hwpstate_pkg_ctrl
tunable to "0" in loader.conf(5).
Intel Speed Shift is Intel's technology to control frequency in hardware,
with hints from software.
Let's get a working version of this in the tree and we can refine it from
here.
Submitted by: bwidawsk, scottph
Reviewed by: bcr (manpages), myself
Discussed with: jhb, kib (earlier versions)
With feedback from: Greg V, gallatin, freebsdnewbie AT freenet.de
Relnotes: yes
Differential Revision: https://reviews.freebsd.org/D18028
