pinctrl: stm32: Use scope based of_node_put() cleanups

Use scope based of_node_put() cleanup to simplify code.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20240504-pinctrl-cleanup-v2-3-26c5f2dc1181@nxp.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>