gpio: sifive: Fix refcount leak in sifive_gpio_probe

In the Linux kernel, the following vulnerability has been resolved:

gpio: sifive: Fix refcount leak in sifive_gpio_probe

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.