MFC 209213:

MFC 209213:
When updating individual CPU's lowest Cx state to use, never set it to a
state lower than the lowest one supported by the current CPU.  This closes
some races with changes to the hw.acpi.cpu_cx_lowest sysctl while Cx
states for individual CPUs were changing (e.g. unplugging the AC adapter
of a laptop) that could result in panics.

Approved by:	re (kib)

git-svn-id: svn://svn.freebsd.org/base/releng/8.1@209473 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f