pinctrl: meson: amlogic-a4: Fix device node reference leak in aml_dt_node_to_map_pinmux()

pinctrl: meson: amlogic-a4: Fix device node reference leak in aml_dt_node_to_map_pinmux()

The of_get_parent() function returns a device_node with an incremented
reference count.

Use the __free(device_node) cleanup attribute to ensure of_node_put()
is automatically called when pnode goes out of scope, fixing a
reference leak.

Fixes: 6e9be3abb78c ("pinctrl: Add driver support for Amlogic SoCs")
Signed-off-by: Felix Gu <ustc.gu@gmail.com>
Signed-off-by: Linus Walleij <linusw@kernel.org>