Document that check_interval set to 0 means no polling.
Noticed by Hidetoshi Seto

Also add a reference from boot options to the sysfs tunables
Acked-by: NHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: NAndi Kleen <ak@linux.intel.com>
Signed-off-by: NHidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>