sched: sched_clock_cpu() based cpu_clock(), lockdep fix

Vegard Nossum reported:

> WARNING: at kernel/lockdep.c:2738 check_flags+0x142/0x160()

which happens due to:

 unsigned long long cpu_clock(int cpu)
 {
         unsigned long long clock;
         unsigned long flags;

         raw_local_irq_save(flags);

as lower level functions can take locks, we must not do that, use
proper lockdep-annotated irq save/restore.
Reported-by: NVegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/sched_clock.c

@@ -250,9 +250,9 @@ unsigned long long cpu_clock(int cpu)
 	unsigned long long clock;
 	unsigned long flags;
 
-	raw_local_irq_save(flags);
+	local_irq_save(flags);
 	clock = sched_clock_cpu(cpu);
-	raw_local_irq_restore(flags);
+	local_irq_restore(flags);
 
 	return clock;
 }