*: 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/ifconfig.c

@@ -10,7 +10,7 @@
  * Authors of the original ifconfig was:
  *              Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
  *
- * 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.
  */
 
 /*