Fix typo in io_u.c::get_next_file()

We should check ops->get_next_file() is TD_F_PROFILE_OPS
is set, not if it's unset.

Signed-off-by: Jens Axboe <axboe@fb.com>
diff --git a/io_u.c b/io_u.c
index e132fd9..997e113 100644
--- a/io_u.c
+++ b/io_u.c
@@ -1100,7 +1100,7 @@
 
 static struct fio_file *get_next_file(struct thread_data *td)
 {
-	if (!(td->flags & TD_F_PROFILE_OPS)) {
+	if (td->flags & TD_F_PROFILE_OPS) {
 		struct prof_io_ops *ops = &td->prof_io_ops;
 
 		if (ops->get_next_file)