doc: allow failure temporarly
Until this lands in rc1:
https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/scripts/kernel-doc?id=bbf00be93e09081ffa06e6fd84ed8f4e469a99d0
The doc build will fail. Mark it as allow_failure temporarily.Edited by Ricardo Ribalda Delgado