Fix typo in comment.

Link: http://lkml.kernel.org/r/1474788764-5774-1-git-send-email-ysxie@foxmail.comSigned-off-by: NYisheng Xie <xieyisheng1@huawei.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>