vlan: add license

pkgs/tools/networking/vlan/default.nix

···
       cp vconfig.8 $out/share/man/man8/
     '';
 
-  meta = {
+  meta = with stdenv.lib; {
     description = "User mode programs to enable VLANs on Ethernet devices";
-    platforms = stdenv.lib.platforms.linux;
+    platforms = platforms.linux;
+    license = licenses.gpl2Plus;
   };
 }