tracing: Drop lock_acquired waittime field

Drop the waittime field from the lock_acquired event, we can
calculate it by substracting the lock_acquired event timestamp
with the matching lock_acquire one.

It is not needed and takes useless space in the traces.

Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Hitoshi Mitake <mitake@dcl.info.waseda.ac.jp>
Cc: Steven Rostedt <rostedt@goodmis.org>
diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 2594e1c..31e22e7 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -3380,7 +3380,7 @@
 		hlock->holdtime_stamp = now;
 	}
 
-	trace_lock_acquired(lock, ip, waittime);
+	trace_lock_acquired(lock, ip);
 
 	stats = get_lock_stats(hlock_class(hlock));
 	if (waittime) {