blktrace: fix output of unknown events

Not all events are pc (packet command) events. An event is a pc
event only if it has BLK_TC_PC bit set.
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NArnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jens Axboe <jens.axboe@oracle.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <49D3236D.3090705@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

kernel/trace/blktrace.c

@@ -1182,7 +1182,7 @@ static enum print_line_t print_one_line(struct trace_iterator *iter,
 	}
 
 	if (unlikely(what == 0 || what >= ARRAY_SIZE(what2act)))
-		ret = trace_seq_printf(s, "Bad pc action %x\n", what);
+		ret = trace_seq_printf(s, "Unknown action %x\n", what);
 	else {
 		ret = log_action(iter, what2act[what].act[long_act]);
 		if (ret)