*: make GNU licensing statement forms more regular

This change retains "or later" state! No licensing _changes_ here,
only form is adjusted (article, space between "GPL" and "v2" and so on).

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/interface.c b/networking/interface.c
index 7c6ed82..83af62b 100644
--- a/networking/interface.c
+++ b/networking/interface.c
@@ -19,7 +19,7 @@
  * Author:      Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
  *              and others.  Copyright 1993 MicroWalt Corporation
  *
- * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
+ * Licensed under GPLv2 or later, see file LICENSE in this source tree.
  *
  * Patched to support 'add' and 'del' keywords for INET(4) addresses
  * by Mrs. Brisby <mrs.brisby@nimh.org>