kernel-doc: Align quick help and the code

The update to the quick help mentions -Wshort-description, but
code never supported for that. Align that with the code by allowing
both: -Wshort-description and -Wshort-desc.

Fixes: 56b0f453 ("kernel-doc: don't let V=1 change outcome")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Link: https://lore.kernel.org/r/20231215150341.1996720-1-andriy.shevchenko@linux.intel.com