PCI/switchtec: Add check of event support

Not all events are supported by every gen/variant of the Switchtec
firmware. To solve this, since Gen4, a new bit in each event header
is introduced to indicate if an event is supported by the firmware.

Link: https://lore.kernel.org/r/20211014141859.11444-6-kelvin.cao@microchip.com


Signed-off-by: Logan Gunthorpe <logang@deltatee.com>
Signed-off-by: Kelvin Cao <kelvin.cao@microchip.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>