ACPI: simplify acpi_pci_irq_del_prt() API

There is no need to pass a segment/bus tuple to this API, as the callsite
always has a struct pci_bus. We can derive segment/bus from the
struct pci_bus, so let's take this opportunit to simplify the API and
make life easier for the callers.

Signed-off-by: Alex Chiang <achiang@hp.com>
Acked-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Signed-off-by: Len Brown <len.brown@intel.com>