irqchip/irq-mvebu-gicp: Fix refcount leak in mvebu_gicp_probe

In the Linux kernel, the following vulnerability has been resolved: irqchip/irq-mvebu-gicp: Fix refcount leak in mvebu_gicp_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.