fsl/fman: Add a missing 'of_node_put()' call in an error handling path

If 'of_phy_find_device()' fails, we must undo the previous 'of_node_get()'
call, as done the the following error handling code.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>