ntfs: remove old debug check for dirty data in ntfs_put_super()

This should not trigger anymore, so kill it.

Acked-by: Anton Altaparmakov <aia21@cam.ac.uk>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>