Add attach and detach methods for SFP buses, which will allow us to get
rid of the netdev storage in sfp-bus.
Signed-off-by: NRussell King <rmk+kernel@armlinux.org.uk>
Reviewed-by: NAndrew Lunn <andrew@lunn.ch>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>