PCI: Remove pci_fixup_cardbus()

Since 1c7f4fe8 ("powerpc/pci: Remove pcibios_setup_bus_devices()")
there's no architecture left setting pci_fixup_cardbus. Therefore remove
support from PCI core.

Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://patch.msgid.link/8de7da4c-2b16-4ee1-8c42-0d04f3c821c6@gmail.com