PCI: cpqphp: Use pci_bus_read_dev_vendor_id() to detect presence

PCI: cpqphp: Use pci_bus_read_dev_vendor_id() to detect presence

The intent of the first part in PCI_RefinedAccessConfig() is to read Vendor
ID register and detect presence of the device that way.

Remove PCI_RefinedAccessConfig() (which was not named very helpfully to
begin with) and replace the call with pci_bus_read_dev_vendor_id() + read
config because it makes the logic more obvious at the caller side.

Link: https://lore.kernel.org/r/20241022091140.3504-3-ilpo.jarvinen@linux.intel.com
Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>