tools: ynl-gen: de-kdocify enums with no doc for entries

tools: ynl-gen: de-kdocify enums with no doc for entries

Sometimes the names of the enum entries are self-explanatory
or come from standards. Forcing authors to write trivial kdoc
for each of such entries seems unreasonable, but kdoc would
complain about undocumented entries.

Detect enums which only have documentation for the entire
type and no documentation for entries. Render their doc
as a plain comment.

Link: https://patch.msgid.link/20241103165314.1631237-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>