This restores the ability of setting bond device's mtu to 9000.

Fixes: 91572088 ("net: use core MTU range checking in core net infra")
Reported-by: daznis@gmail.com
Reported-by: Brad Campbell <lists2009@fnarfbargle.com>
Cc: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>