memory: tegra: Add a missing 'of_node_put()' call

If 'of_find_device_by_node()' fails, an 'of_node_put()' call is missing in
the error handling path.
Fix it by reordering the code.

While at it, remove some empty lines in a more or less similar construction
a few lines below.

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Thierry Reding <treding@nvidia.com>