irqdomain: Add parent field to struct irqchip_fwid

irqdomain: Add parent field to struct irqchip_fwid

The GICv5 driver IRQ domain hierarchy requires adding a parent field to
struct irqchip_fwid so that core code can reference a fwnode_handle parent
for a given fwnode.

Add a parent field to struct irqchip_fwid and update the related kernel API
functions to initialize and handle it.

Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Jonathan Cameron <jonathan.cameron@huawei.com>
Acked-by: Thomas Gleixner <tglx@kernel.org>
Link: https://patch.msgid.link/20260115-gicv5-host-acpi-v3-1-c13a9a150388@kernel.org
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>