tracing: Fix lockdep warning in global_clock()

# echo 1 > events/enable
 # echo global > trace_clock

------------[ cut here ]------------
WARNING: at kernel/lockdep.c:3162 check_flags+0xb2/0x190()
...
---[ end trace 3f86734a89416623 ]---
possible reason: unannotated irqs-on.
...

There's no reason to use the raw_local_irq_save() in trace_clock_global.
The local_irq_save() version is fine, and does not cause the bug in lockdep.
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
LKML-Reference: <4BA97FA1.7030606@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

kernel/trace/trace_clock.c

@@ -84,7 +84,7 @@ u64 notrace trace_clock_global(void)
 	int this_cpu;
 	u64 now;
 
-	raw_local_irq_save(flags);
+	local_irq_save(flags);
 
 	this_cpu = raw_smp_processor_id();
 	now = cpu_clock(this_cpu);
@@ -110,7 +110,7 @@ u64 notrace trace_clock_global(void)
 	arch_spin_unlock(&trace_clock_struct.lock);
 
  out:
-	raw_local_irq_restore(flags);
+	local_irq_restore(flags);
 
 	return now;
 }