PCI: microchip: Add get_events() callback and PLDA get_event()

PCI: microchip: Add get_events() callback and PLDA get_event()

As PLDA DT binding doc (Documentation/devicetree/bindings/pci/
plda,xpressrich3-axi-common.yaml) showed, PLDA PCIe contains an interrupt
controller.

PolarFire implements its own PCIe interrupts, additional to the regular
PCIe interrupts, due to lack of an MSI controller, so the interrupt to
event number mapping is different to the PLDA regular interrupts,
necessitating a custom get_events() implementation.

Microchip PolarFire PCIe additional interrupts (defined in
drivers/pci/controller/plda/pcie-microchip-host.c):

  EVENT_PCIE_L2_EXIT
  EVENT_PCIE_HOTRST_EXIT
  EVENT_PCIE_DLUP_EXIT
  EVENT_SEC_TX_RAM_SEC_ERR
  EVENT_SEC_RX_RAM_SEC_ERR
  ...

plda_get_events() adds interrupt register to PLDA event num mapping codes.
All the PLDA interrupts can be seen in new added graph.

[kwilczynski: commit log]
Link: https://lore.kernel.org/linux-pci/20240328091835.14797-15-minda.chen@starfivetech.com
Signed-off-by: Minda Chen <minda.chen@starfivetech.com>
Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>