Fix bond_destroy and bond_free_all to not reference the struct
net_device after calling unregister_netdevice.

Bug and offending change reported by Moni Shoua <monis@voltaire.com>
Signed-off-by: NJay Vosburgh <fubar@us.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>