docs: clearing-warn-once.txt: add a title for this document

This document misses a title. Add it, in order to follow
the documentation standard.

Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This commit is contained in:
Mauro Carvalho Chehab 2019-04-10 06:56:22 -03:00 • committed by Jonathan Corbet
commit 26187d18b8