PCI: Simplify pci_create_slot() logic

Simplify pci_create_slot() by splitting an "if" statement into two parts.
In order to not duplicate error handling, add a new label to handle kobj
put.

Link: https://lore.kernel.org/r/20241004152240.7926-1-ilpo.jarvinen@linux.intel.com


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