locking/lockdep: Only ask for /proc/lock_stat output when available

When lockdep turns itself off, the following message is logged:

Please attach the output of /proc/lock_stat to the bug report

Omit this message when CONFIG_LOCK_STAT is off, and /proc/lock_stat
doesn't exist.

Signed-off-by: Andreas Gruenbacher <[e-mail]>
Signed-off-by: Peter Zijlstra <[e-mail]>
Cc: Linus Torvalds <[e-mail]>
Link: http://lkml.kernel.org/r/[e-mail]
Signed-off-by: Ingo Molnar <[e-mail]>

kernel/locking/lockdep.c

···
 {
 	printk(KERN_DEBUG "%s\n", bug_msg);
 	printk(KERN_DEBUG "turning off the locking correctness validator.\n");
+#ifdef CONFIG_LOCK_STAT
 	printk(KERN_DEBUG "Please attach the output of /proc/lock_stat to the bug report\n");
+#endif
 }
 
 static int save_trace(struct stack_trace *trace)