fuse: fix weird page warning

When PageWaiters was added, updating this check was missed.

Reported-by: Nikolaus Rath <Nikolaus@rath.org>
Reported-by: Hugh Dickins <hughd@google.com>
Fixes: 62906027

 ("mm: add PageWaiters indicating tasks are waiting for a page bit")
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>