net: sfp: constify sfp-bus internal fwnode uses

Constify sfp-bus internal fwnode uses, since we do not modify the
fwnode structures.

Signed-off-by: Russell King (Oracle) <[e-mail]>
Reviewed-by: Simon Horman <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/phy/sfp-bus.c

···
 	/* private: */
 	struct kref kref;
 	struct list_head node;
-	struct fwnode_handle *fwnode;
+	const struct fwnode_handle *fwnode;
 
 	const struct sfp_socket_ops *socket_ops;
 	struct device *sfp_dev;
···
 	return bus->registered ? bus->upstream_ops : NULL;
 }
 
-static struct sfp_bus *sfp_bus_get(struct fwnode_handle *fwnode)
+static struct sfp_bus *sfp_bus_get(const struct fwnode_handle *fwnode)
 {
 	struct sfp_bus *sfp, *new, *found = NULL;