sched: Add #ifdef around irq time accounting functions

Get rid of this:

 kernel/sched.c:3731:13: warning: 'irqtime_account_idle_ticks' defined but not used
 kernel/sched.c:3732:13: warning: 'irqtime_account_process_tick' defined but not used

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Venkatesh Pallipadi <venki@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
LKML-Reference: <20110225133228.GD7469@osiris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

Author: heicarst

kernel/sched.c

@@ -3687,6 +3687,7 @@ void account_system_time(struct task_struct *p, int hardirq_offset,
 	__account_system_time(p, cputime, cputime_scaled, target_cputime64);
 }
 
+#ifndef CONFIG_VIRT_CPU_ACCOUNTING
 #ifdef CONFIG_IRQ_TIME_ACCOUNTING
 /*
  * Account a tick to a process and cpustat
@@ -3753,6 +3754,7 @@ static void irqtime_account_idle_ticks(int ticks) {}
 static void irqtime_account_process_tick(struct task_struct *p, int user_tick,
 						struct rq *rq) {}
 #endif
+#endif /* !CONFIG_VIRT_CPU_ACCOUNTING */
 
 /*
  * Account for involuntary wait time.