sched, autogroup, sysctl: Use proc_dointvec_minmax() instead

sched_autogroup_enabled has min/max value, proc_dointvec_minmax() is
be used for this case.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <1298185696-4403-2-git-send-email-yong.zhang0@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>