mtd: partitions: Fix refcount leak in parse_redboot_of

mtd: partitions: Fix refcount leak in parse_redboot_of

of_get_child_by_name() returns a node pointer with refcount
incremented, we should use of_node_put() on it when not need anymore.
Add missing of_node_put() to avoid refcount leak.

Fixes: f0e4c7650b8f ("mtd: partitions: redboot: seek fis-index-block in the right node")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20220526110652.64849-1-linmq006@gmail.com