scripts/kernel-doc: add internal hyperlink to DOC: sections

While DOC: section titles are not converted into RST headings
sections and are only decorated with strong emphasis markup,
nothing stops us from generating internal hyperlinks for them,
to mimic implicit hyperlinks to RST headings.
Signed-off-by: NMichal Wajdeczko <michal.wajdeczko@intel.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://lore.kernel.org/r/20210118110813.1490-1-michal.wajdeczko@intel.comSigned-off-by: NJonathan Corbet <corbet@lwn.net>

scripts/kernel-doc

@@ -836,6 +836,7 @@ sub output_blockhead_rst(%) {
 	next if (defined($nosymbol_table{$section}));
 
 	if ($output_selection != OUTPUT_INCLUDE) {
+	    print ".. _$section:\n\n";
 	    print "**$section**\n\n";
 	}
         print_lineno($section_start_lines{$section});