PCI: mediatek: Fix a leaked reference by adding missing of_node_put()

The call to of_get_next_child() returns a node pointer with refcount
incremented thus it must be explicitly decremented after the last
usage.

irq_domain_add_linear() also calls of_node_get() to increase refcount,
so irq_domain will not be affected when it is released.

Detected by coccinelle with the following warnings:
  ./drivers/pci/controller/pcie-mediatek.c:577:2-8: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 567, but without a corresponding object release within this function.
  ./drivers/pci/controller/pcie-mediatek.c:583:3-9: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 567, but without a corresponding object release within this function.
  ./drivers/pci/controller/pcie-mediatek.c:586:1-7: ERROR: missing of_node_put; acquired a node pointer with refcount incremented on line 567, but without a corresponding object release within this function.

Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Acked-by: Honghui Zhang <honghui.zhang@mediatek.com>
Cc: Ryder Lee <ryder.lee@mediatek.com>
Cc: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>
Cc: Matthias Brugger <matthias.bgg@gmail.com>
Cc: linux-pci@vger.kernel.org
Cc: linux-mediatek@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linux-arm-kernel@lists.infradead.org

drivers/pci/controller/pcie-mediatek.c

@@ -578,6 +578,7 @@ static int mtk_pcie_init_irq_domain(struct mtk_pcie_port *port,
 
 	port->irq_domain = irq_domain_add_linear(pcie_intc_node, PCI_NUM_INTX,
 						 &intx_domain_ops, port);
+	of_node_put(pcie_intc_node);
 	if (!port->irq_domain) {
 		dev_err(dev, "failed to get INTx IRQ domain\n");
 		return -ENODEV;