PCI: mediatek: Fix IRQ domain leak when port fails to enable

In the Linux kernel, the following vulnerability has been resolved: PCI: mediatek: Fix IRQ domain leak when port fails to enable When mtk_pcie_enable_port() fails, mtk_pcie_port_free() removes the port from pcie->ports and frees the port structure. However, the IRQ domains set up earlier by mtk_pcie_init_irq_domain() are never freed. Fix this by refactoring mtk_pcie_irq_teardown() into a per-port helper, mtk_pcie_irq_teardown_port(), and calling it from mtk_pcie_setup() when mtk_pcie_enable_port() fails. Since the IRQ teardown must only happen in the probe error path (during resume, child devices may have active MSI mappings and the NOIRQ context prohibits sleeping locks), mtk_pcie_enable_port() is changed to return an error code so callers can distinguish the two paths and act accordingly. This issue was reported by Sashiko while reviewing the EcoNet EN7528 SoC support series.