sched: idle_at_tick is only used when CONFIG_SMP is set

Impact: struct rq size optimization

The idle_at_tick in struct rq is only used in SMP settings
and it does not make sense to have this in the rq in an UP setup.

Signed-off-by: Henrik Austad <henrik@austad.us>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/sched.c b/kernel/sched.c
index 5faf5d4..648154c 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -555,7 +555,6 @@
 	unsigned long nr_running;
 	#define CPU_LOAD_IDX_MAX 5
 	unsigned long cpu_load[CPU_LOAD_IDX_MAX];
-	unsigned char idle_at_tick;
 #ifdef CONFIG_NO_HZ
 	unsigned long last_tick_seen;
 	unsigned char in_nohz_recently;
@@ -596,6 +595,7 @@
 	struct root_domain *rd;
 	struct sched_domain *sd;
 
+	unsigned char idle_at_tick;
 	/* For active balancing */
 	int active_balance;
 	int push_cpu;