sfp: fix module initialisation with netdev already up

It was been observed that with a particular order of initialisation,
the netdev can be up, but the SFP module still has its TX_DISABLE
signal asserted.  This occurs when the network device brought up before
the SFP kernel module has been inserted by userspace.

This occurs because sfp-bus layer does not hear about the change in
network device state, and so assumes that it is still down.  Set
netdev->sfp when the upstream is registered to work around this problem.
Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/phy/sfp-bus.c

@@ -349,7 +349,6 @@ static int sfp_register_bus(struct sfp_bus *bus)
 	}
 	if (bus->started)
 		bus->socket_ops->start(bus->sfp);
-	bus->netdev->sfp_bus = bus;
 	bus->registered = true;
 	return 0;
 }
@@ -364,7 +363,6 @@ static void sfp_unregister_bus(struct sfp_bus *bus)
 		if (bus->phydev && ops && ops->disconnect_phy)
 			ops->disconnect_phy(bus->upstream);
 	}
-	bus->netdev->sfp_bus = NULL;
 	bus->registered = false;
 }
 
@@ -440,6 +438,7 @@ static void sfp_upstream_clear(struct sfp_bus *bus)
 {
 	bus->upstream_ops = NULL;
 	bus->upstream = NULL;
+	bus->netdev->sfp_bus = NULL;
 	bus->netdev = NULL;
 }
 
@@ -468,6 +467,7 @@ struct sfp_bus *sfp_register_upstream(struct fwnode_handle *fwnode,
 		bus->upstream_ops = ops;
 		bus->upstream = upstream;
 		bus->netdev = ndev;
+		ndev->sfp_bus = bus;
 
 		if (bus->sfp) {
 			ret = sfp_register_bus(bus);