PCI: microchip: Add num_events field to struct plda_pcie_rp

PCI: microchip: Add num_events field to struct plda_pcie_rp

The number of events is different across platforms. In order to share
interrupt processing code, add a variable that defines the number of
events so that it can be set per-platform instead of hardcoding it.

Link: https://lore.kernel.org/linux-pci/20240328091835.14797-12-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>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>