sched: Remove redundant CONFIG_CGROUP_SCHED ifdef

CONFIG_[FAIR|RT]_GROUP_SCHED always means CONFIG_CGROUP_SCHED

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
LKML-Reference: <1293803938-8157-1-git-send-email-yong.zhang0@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>