irqchip/apple-aic: Fix refcount leak in build_fiq_affinity

In the Linux kernel, the following vulnerability has been resolved: irqchip/apple-aic: Fix refcount leak in build_fiq_affinity of_find_node_by_phandle() returns a node pointer with refcount incremented, we should use of_node_put() on it when not need anymore. Add missing of_node_put() to avoid refcount leak.