PCI: switchtec: Add support for PCIe Gen5 devices

Advertise support of Gen5 devices in the driver's device ID table and
add the same IDs for the switchtec quirks. Also update driver code to
accommodate them.

Link: https://lore.kernel.org/r/20230624000003.2315364-3-kelvin.cao@microchip.com
Signed-off-by: Kelvin Cao <kelvin.cao@microchip.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Reviewed-by: Logan Gunthorpe <logang@deltatee.com>