PCI: Track Flit Mode Status & print it with link status

PCI: Track Flit Mode Status & print it with link status

PCIe r6.0 added Flit mode, which mainly alters HW behavior, but there are
some OS visible changes. The OS visible changes include differences in the
layout of some capabilities and interpretation of the TLP headers (in
diagnostics situations).

To be able to determine which mode the PCIe Link is using, store the Flit
Mode Status (PCIe r6.1 sec 7.5.3.20) information in addition to the Link
speed into struct pci_bus in pcie_update_link_speed().

Link: https://lore.kernel.org/r/20250207161836.2755-2-ilpo.jarvinen@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
[bhelgaas: use unsigned int:1 instead of bool, update flit_mode setting]
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>