Useful to workaround C3 ipw2100 packet loss,
reducing noise or boot issues on some models.
http://bugme.osdl.org/show_bug.cgi?id=3549

For static processor driver, boot cmdline:
processor.acpi_cstate_limit=2

For processor module, /etc/modprobe.conf:
options processor acpi_cstate_limit=2

For manual processor module load:
# modprobe processor acpi_cstate_limit=2

From kernel or kernel module:
#include <linux/acpi.h>
acpi_set_cstate_limit(2);

Inspired by patches from Jos Delbar and Andi Kleen
Signed-off-by: Len Brown <len.brown@intel.com>