Some SoCs have the limitation that PME/AER can't work over MSI. And
vendors route the AER/PME via the dedicated SPI interrupt which is only
handled by the controller driver.

Add the generic get_service_irqs() callback for bridge, to let portdrv
can fetch the vendor specific AER/PME interrupter by it.

Closes: https://lore.kernel.org/linux-pci/20250702223841.GA1905230@bhelgaas/
Tested on LS1046A RDB board, the AER interrupter can be triggered by
pull-out of EP device based on v6.16 kernel.

[PATCH v1 1/2] PCI/portdrv: Use get_service_irqs() callback to get
[PATCH v1 2/2] PCI: dwc: Fetch dedicated AER/PME interrupters

drivers/pci/controller/dwc/pcie-designware-host.c | 32 ++++++++++++++++++++++++++++++++
drivers/pci/pcie/portdrv.c                        |  7 +++++++
include/linux/pci.h                               |  1 +