*: 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/ether-wake.c b/networking/ether-wake.c
index deeb68c..121f153 100644
--- a/networking/ether-wake.c
+++ b/networking/ether-wake.c
@@ -2,7 +2,7 @@
 /*
  * ether-wake.c - Send a magic packet to wake up sleeping machines.
  *
- * 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.
  *
  * Author:      Donald Becker, http://www.scyld.com/"; http://www.scyld.com/wakeonlan.html
  * Busybox port: Christian Volkmann <haveaniceday@online.de>