checkpatch: only flag FSF address, not gnu.org URL

This change restricts the check for the for the FSF address in the GPL
copyright statement so that it only flags the address, not the
references to the gnu.org/licenses URL which appears to be used in
numerous drivers.  The idea is to still allow some reference to an
external copy of the GPL in the event that files are copied out of the
kernel tree without the COPYING file.

So for example this statement will still return an error:
  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.

However, this statement will not return an error after this patch:
  You should have received a copy of the GNU General Public License
  along with this program.  If not, see <http://www.gnu.org/licenses/

>.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Cc: Joe Perches <joe@perches.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>