scripts: kernel-doc: Relink argument parsing error handling to pod2usage

The former usage function is substituted, although not as the -h and -help
parameter handler yet.

Purpose: Use Pod::Usage to handle documentation printing in an integrated
way.

Signed-off-by: Tomasz Warniełło <tomasz.warniello@gmail.com>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org>
Disliked-by: Akira Yokosawa <akiyks@gmail.com>
Link: https://lore.kernel.org/r/20220218181628.1411551-3-tomasz.warniello@gmail.com


Signed-off-by: Jonathan Corbet <corbet@lwn.net>