PCI: Execute quirk_enable_clear_retrain_link() earlier

Make quirk_enable_clear_retrain_link() an early quirk so that any later
fixups can rely on dev->clear_retrain_link to have been already
initialised.

[bhelgaas: reorder to just before it becomes possible to call
pcie_retrain_link() earlier]
Link: https://lore.kernel.org/r/alpine.DEB.2.21.2305310049000.59226@angie.orcam.me.uk
Signed-off-by: Maciej W. Rozycki <macro@orcam.me.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>