pinctrl: stm32: Fix refcount leak in stm32_pctrl_get_irq_domain

pinctrl: stm32: Fix refcount leak in stm32_pctrl_get_irq_domain

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

Fixes: d86f4d71e42a ("pinctrl: stm32: check irq controller availability at probe")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Link: https://lore.kernel.org/r/20230102082503.3944927-1-linmq006@gmail.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>