sched: fix SCHED_HRTICK dependency

Currently, it seems SCHED_HRTICK allowed for !SMP. But, it seems to have
no dependency of it. Fix it.

Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Ingo Molnar <mingo@elte.hu>