cfq: fix the log message after dispatched a request

The blktrace tools can show process id when cfq dispatched a request,
using cfq_log_cfqq() instead of cfq_log().
Signed-off-by: NShan Wei <shanwei@cn.fujitsu.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

block/cfq-iosched.c

@@ -1349,7 +1349,7 @@ static int cfq_dispatch_requests(struct request_queue *q, int force)
 		cfq_slice_expired(cfqd, 0);
 	}
 
-	cfq_log(cfqd, "dispatched a request");
+	cfq_log_cfqq(cfqd, cfqq, "dispatched a request");
 	return 1;
 }