USB: option: blacklist network interface on Huawei E1820

The mode used by Windows for the Huawei E1820 will use the
same ff/ff/ff class codes for both serial and network
functions.

Reported-by: Graham Inggs <graham.inggs@uct.ac.za>
Signed-off-by: Bjørn Mork <bjorn@mork.no>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>