crypto: replace FSF address with web source in license notices

A few years ago the FSF moved and "59 Temple Place" is wrong. Having this
still in our source files feels old and unmaintained.

Let's take the license statement serious and not confuse users.

As https://www.gnu.org/licenses/gpl-howto.html suggests, we replace the
postal address with "<http://www.gnu.org/licenses/>".

Signed-off-by: Martin Kepplinger <martink@posteo.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

crypto/twofish_generic.c

@@ -23,9 +23,8 @@
  * GNU General Public License for more details.
  * 
  * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307
- * USA
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
  *
  * This code is a "clean room" implementation, written from the paper
  * _Twofish: A 128-Bit Block Cipher_ by Bruce Schneier, John Kelsey,