VALID_PAGE() has been removed from kernel long time ago,
so fix the comment.
Signed-off-by: NJiang Liu <jiang.liu@huawei.com>
Acked-by: NGuan Xuetao <gxt@mprc.pku.edu.cn>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>