*: 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>

networking/libiproute/utils.c

@@ -2,7 +2,7 @@
 /*
  * utils.c
  *
- * 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.
  *
  * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
  *