gpio: sifive: Fix refcount leak in sifive_gpio_probe

[ Upstream commit 694175cd ]

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: 96868dce

 ("gpio/sifive: Add GPIO driver for SiFive SoCs")
Signed-off-by: Miaoqian Lin <linmq006@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>