pinctrl: sirf: atlas7: Add missing 'of_node_put()'

Reference to 'sys2pci_np' should be dropped in all cases here, not only in
error handling path.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>