Enable xref broken warnings. While here, change the output to only show cross-references, as there's no need to show the entire cec.h header at the docs. Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org> Signed-off-by: Jonathan Corbet <corbet@lwn.net> Message-ID: <c587872ca3685213d9f8e88277404c9e253633df.1759329363.git.mchehab+huawei@kernel.org>