doc-guide: kernel-doc: add %CONST examples

Add examples of using '%' for formatting constant values to
facilitate more usage of "%CONST" in kernel-doc.

Suggested-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20251104050930.720711-1-rdunlap@infradead.org>

Author: rddunlap

Documentation/doc-guide/kernel-doc.rst

@@ -405,6 +405,10 @@ Domain`_ references.
 ``%CONST``
   Name of a constant. (No cross-referencing, just formatting.)
 
+  Examples::
+
+    %0    %NULL    %-1    %-EFAULT    %-EINVAL    %-ENOMEM
+
 ````literal````
   A literal block that should be handled as-is. The output will use a
   ``monospaced font``.