mtd: maps: Fix refcount leak in ap_flash_init

mtd: maps: Fix refcount leak in ap_flash_init

of_find_matching_node() 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: b0afd44bc192 ("mtd: physmap_of: add a hook for Versatile write protection")
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/20220523143255.4376-1-linmq006@gmail.com