net: fman: Clean up error handling

This removes the _return label, since something like

	err = -EFOO;
	goto _return;

can be replaced by the briefer

	return -EFOO;

Additionally, this skips going to _return_of_node_put when dev_node has
already been put (preventing a double put).

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Acked-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>