sched: Fix UP build breakage

The recent cgroup-scheduling rework caused a UP build problem.

Cc: Paul Turner <pjt@google.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/sched_fair.c

@@ -562,7 +562,7 @@ __update_curr(struct cfs_rq *cfs_rq, struct sched_entity *curr,
 	curr->vruntime += delta_exec_weighted;
 	update_min_vruntime(cfs_rq);
 
-#ifdef CONFIG_FAIR_GROUP_SCHED
+#if defined CONFIG_SMP && defined CONFIG_FAIR_GROUP_SCHED
 	cfs_rq->load_unacc_exec_time += delta_exec;
 	if (cfs_rq->load_unacc_exec_time > sysctl_sched_shares_window) {
 		update_cfs_load(cfs_rq, 0);