The struct devlink_port_attrs holds the attributes of devlink_port.

Similarly to the previous patch, 'switch_port' attribute is another
exception.

Move 'switch_port' to be devlink_port's field.
Signed-off-by: NDanielle Ratson <danieller@mellanox.com>
Reviewed-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>