tracing: fix a build error on alpha

Impact: build fix on Alpha

When tracing is enabled, some arch have included <linux/irqflags.h>
on their <asm/system.h> but others like alpha or m68k don't.

Build error on alpha:

kernel/trace/trace.c: In function 'tracing_cpumask_write':
kernel/trace/trace.c:2145: error: implicit declaration of function 'raw_local_irq_disable'
kernel/trace/trace.c:2162: error: implicit declaration of function 'raw_local_irq_enable'

Tested on Alpha through a cross-compiler (should correct a similar issue on m68k).

Reported-by: Alexey Dobriyan <[e-mail]>
Signed-off-by: Frederic Weisbecker <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

kernel/trace/trace.c

···
 
 #include <linux/stacktrace.h>
 #include <linux/ring_buffer.h>
+#include <linux/irqflags.h>
 
 #include "trace.h"