sunvnet: vnet_port_remove must call unregister_netdev

[ Upstream commit aabb9875d02559ab9b928cd6f259a5cc4c21a589 ]

The missing call to unregister_netdev() leaves the interface active
after the driver is unloaded by rmmod.

Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>