PCI: Indicate optional resource assignment failures

Add pci_dbg() to note that an assignment failure was for an optional
resource and reword existing message about resource resize to say the
change was optional.

Link: https://lore.kernel.org/r/20241216175632.4175-22-ilpo.jarvinen@linux.intel.com


Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Tested-by: Xiaochun Lee <lixc17@lenovo.com>