Use IOAPIC PCI rid as the interrupt TLP source id for DMAR interrupt
remapping.

VT-d specification requires use of PCI rid as source id for IOAPICs
enumerated by PCI bus. The values from the DMAR ACPI table should be
only used when IOAPIC is not on PCI.

Reviewed by: jhb
Sponsored by: The FreeBSD Foundation
Hardware provided by: Intel
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D12205