MINOR: dynbuf: use regular lists instead of mt_lists for buffer_wait

There's no point anymore in keeping mt_lists for the buffer_wait and
buffer_wq since it's thread-local now.
diff --git a/src/check.c b/src/check.c
index ff4effa..6451dcf 100644
--- a/src/check.c
+++ b/src/check.c
@@ -1015,11 +1015,11 @@
 {
 	struct buffer *buf = NULL;
 
-	if (likely(!MT_LIST_ADDED(&check->buf_wait.list)) &&
+	if (likely(!LIST_ADDED(&check->buf_wait.list)) &&
 	    unlikely((buf = b_alloc_margin(bptr, 0)) == NULL)) {
 		check->buf_wait.target = check;
 		check->buf_wait.wakeup_cb = check_buf_available;
-		MT_LIST_ADDQ(&ti->buffer_wq, &check->buf_wait.list);
+		LIST_ADDQ(&ti->buffer_wq, &check->buf_wait.list);
 	}
 	return buf;
 }
@@ -1042,7 +1042,7 @@
 
 	check->bi = BUF_NULL;
 	check->bo = BUF_NULL;
-	MT_LIST_INIT(&check->buf_wait.list);
+	LIST_INIT(&check->buf_wait.list);
 
 	check->wait_list.tasklet = tasklet_new();
 	if (!check->wait_list.tasklet)