dsa: move devlink_port_attrs_set() call before register

Since attrs are static during the existence of devlink port, set the
before registration of the port.

Signed-off-by: Jiri Pirko <jiri@mellanox.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>