scripts: kernel-doc: support private / public marking for enums

Enums benefit from private markings, too. For netlink attribute
name enums always end with a pair of __$n_MAX and $n_MAX members.
Documenting them feels a bit tedious.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Randy Dunlap <rdunlap@infradead.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
Message-ID: <20230621223525.2722703-1-kuba@kernel.org>

scripts/kernel-doc

@@ -1301,6 +1301,9 @@ sub dump_enum($$) {
     my $file = shift;
     my $members;
 
+    # ignore members marked private:
+    $x =~ s/\/\*\s*private:.*?\/\*\s*public:.*?\*\///gosi;
+    $x =~ s/\/\*\s*private:.*}/}/gosi;
 
     $x =~ s@/\*.*?\*/@@gos;	# strip comments.
     # strip #define macros inside enums