irqchip/gic-v2m: Prevent use after free of gicv2m_get_fwnode()

In the Linux kernel, the following vulnerability has been resolved: irqchip/gic-v2m: Prevent use after free of gicv2m_get_fwnode() With ACPI in place, gicv2m_get_fwnode() is registered with the pci subsystem as pci_msi_get_fwnode_cb(), which may get invoked at runtime during a PCI host bridge probe. But, the call back is wrongly marked as __init, causing it to be freed, while being registered with the PCI subsystem and could trigger: Unable to handle kernel paging request at virtual address ffff8000816c0400 gicv2m_get_fwnode+0x0/0x58 (P) pci_set_bus_msi_domain+0x74/0x88 pci_register_host_bridge+0x194/0x548 This is easily reproducible on a Juno board with ACPI boot. Retain the function for later use.