Merge branch 'for-4.15/timer' into for-linus

Post initial pull timer related changes for block drivers. Not merged
with the first pull, since they were dependent on this commit in
mainline:

commit 686fef928bba6be13cabe639f154af7d72b63120
Author: Kees Cook <keescook@chromium.org>
Date:   Thu Sep 28 06:38:17 2017 -0700

    timer: Prepare to change timer callback argument type