usb gadget: clean up FSF boilerplate text

remove the following two paragraphs as they are not needed:

This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the 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.

Signed-off-by: Klaus Schwarzkopf <schwarzkopf@sensortherm.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>