PCI: mediatek-gen3: Prevent leaking IRQ domains when IRQ not found

In mtk_pcie_setup_irq(), the IRQ domains are allocated before the
controller's IRQ is fetched. If the latter fails, the function
directly returns an error, without cleaning up the allocated domains.

Hence, reverse the order so that the IRQ domains are allocated after the
controller's IRQ is found.

This was flagged by Sashiko during a review of "[PATCH v6 0/7] PCI:
mediatek-gen3: add power control support".

Fixes: 814ccee ("PCI: mediatek-gen3: Add INTx support")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Signed-off-by: Manivannan Sadhasivam <mani@kernel.org>
Link: https://sashiko.dev/#/patchset/20260324052002.4072430-1-wenst%40chromium.org
Link: https://patch.msgid.link/20260324093542.18523-1-wenst@chromium.org

Author: wens

drivers/pci/controller/pcie-mediatek-gen3.c

@@ -890,14 +890,14 @@ static int mtk_pcie_setup_irq(struct mtk_gen3_pcie *pcie)
 	struct platform_device *pdev = to_platform_device(dev);
 	int err;
 
-	err = mtk_pcie_init_irq_domains(pcie);
-	if (err)
-		return err;
-
 	pcie->irq = platform_get_irq(pdev, 0);
 	if (pcie->irq < 0)
 		return pcie->irq;
 
+	err = mtk_pcie_init_irq_domains(pcie);
+	if (err)
+		return err;
+
 	irq_set_chained_handler_and_data(pcie->irq, mtk_pcie_irq_handler, pcie);
 
 	return 0;