docs: automarkup: Mark up undocumented entities too

docs: automarkup: Mark up undocumented entities too

The automarkup code generates markup and a cross-reference link for
functions, structs, etc. for which it finds kerneldoc documentation.
Undocumented entities are left untouched; that creates an inconsistent
reading experience and has caused some writers to go to extra measures to
cause the markup to happen.

Mark up detected C entities regardless of whether they are documented.

Reviewed-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>