ARM: cns3xxx: Fix refcount leak in cns3xxx_init

of_find_compatible_node() returns a node pointer with refcount
incremented, we should use of_node_put() on it when done.
Add missing of_node_put() to avoid refcount leak.

Fixes: 415f5914 ("ARM: cns3xxx: initial DT support")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Acked-by: Krzysztof Halasa <khalasa@piap.pl>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>