docs: kdoc: Coalesce parameter-list handling

docs: kdoc: Coalesce parameter-list handling

Callers to output_declaration() always pass the parameter information from
self.entry; remove all of the boilerplate arguments and just get at that
information directly.  Formalize its placement in the KdocItem class.

It would be nice to get rid of parameterlist as well, but that has the
effect of reordering the output of function parameters and struct fields to
match the order in the kerneldoc comment rather than in the declaration.
One could argue about which is more correct, but the ordering has been left
unchanged for now.

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