PCI: Remove unused function declarations

PCI: Remove unused function declarations

The following declarations have never been implemented since the beginning
of git history, so remove them:

  u8 acpiphp_get_attention_status(struct acpiphp_slot *slot);
  u8 cpci_get_latch_status(struct slot *slot);
  u8 cpci_get_adapter_status(struct slot *slot);
  int ibmphp_get_total_hp_slots(void);
  void ibmphp_free_ibm_slot(struct slot *);
  void pdev_enable_device(struct pci_dev *);

Link: https://lore.kernel.org/r/20230811095933.28652-1-yuehaibing@huawei.com
Signed-off-by: Yue Haibing <yuehaibing@huawei.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>