PCI: rcar-host: Pass proper IRQ domain to generic_handle_domain_irq()

In the Linux kernel, the following vulnerability has been resolved: PCI: rcar-host: Pass proper IRQ domain to generic_handle_domain_irq() Starting with commit dd26c1a23fd5 ("PCI: rcar-host: Switch to msi_create_parent_irq_domain()"), the MSI parent IRQ domain is NULL because the object of type struct irq_domain_info passed to: msi_create_parent_irq_domain() -> irq_domain_instantiate()() -> __irq_domain_instantiate() has no reference to the parent IRQ domain. Using msi->domain->parent as an argument for generic_handle_domain_irq() leads to below error: "Unable to handle kernel NULL pointer dereference at virtual address" This error was identified while switching the upcoming RZ/G3S PCIe host controller driver to msi_create_parent_irq_domain() (which was using a similar pattern to handle MSIs (see link section)), but it was not tested on hardware using the pcie-rcar-host controller driver due to lack of hardware. [mani: reworded subject and description]