x86/irq: Add allocation type for parent domain retrieval

irq_remapping_ir_irq_domain() is used to retrieve the remapping parent
domain for an allocation type. irq_remapping_irq_domain() is for retrieving
the actual device domain for allocating interrupts for a device.

The two functions are similar and can be unified by using explicit modes
for parent irq domain retrieval.

Add X86_IRQ_ALLOC_TYPE_IOAPIC/HPET_GET_PARENT and use it in the iommu
implementations. Drop the parent domain retrieval for PCI_MSI/X as that is
unused.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Joerg Roedel <jroedel@suse.de>
Link: https://lore.kernel.org/r/20200826112331.436350257@linutronix.de

diff --git a/drivers/iommu/hyperv-iommu.c b/drivers/iommu/hyperv-iommu.c
index 8919c1c..e7bee11 100644
--- a/drivers/iommu/hyperv-iommu.c
+++ b/drivers/iommu/hyperv-iommu.c
@@ -184,7 +184,7 @@ static int __init hyperv_enable_irq_remapping(void)
 
 static struct irq_domain *hyperv_get_ir_irq_domain(struct irq_alloc_info *info)
 {
-	if (info->type == X86_IRQ_ALLOC_TYPE_IOAPIC)
+	if (info->type == X86_IRQ_ALLOC_TYPE_IOAPIC_GET_PARENT)
 		return ioapic_ir_domain;
 	else
 		return NULL;