sched: sched_clock() lockdep fix

Sitsofe Wheeler bisected the following commit to cause a lockdep to
warn about itself and turn itself off:

> commit c6531cc
> Author: Ingo Molnar <mingo@elte.hu>
> Date:   Mon May 12 21:21:14 2008 +0200
>
>     sched: do not trace sched_clock

do not use raw irq flags in cpu_clock() as it causes lockdep to lose
track of the true state of the IRQ flag.

Reported-and-bisected-by: Sitsofe Wheeler <sitsofe@yahoo.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

kernel/sched.c

@@ -889,7 +889,7 @@ unsigned long long notrace cpu_clock(int cpu)
 	unsigned long long prev_cpu_time, time, delta_time;
 	unsigned long flags;
 
-	raw_local_irq_save(flags);
+	local_irq_save(flags);
 	prev_cpu_time = per_cpu(prev_cpu_time, cpu);
 	time = __cpu_clock(cpu) + per_cpu(time_offset, cpu);
 	delta_time = time-prev_cpu_time;
@@ -898,7 +898,7 @@ unsigned long long notrace cpu_clock(int cpu)
 		time = __sync_cpu_clock(time, cpu);
 		per_cpu(prev_cpu_time, cpu) = time;
 	}
-	raw_local_irq_restore(flags);
+	local_irq_restore(flags);
 
 	return time;
 }