Where are the pci_read_config_* and pci_write_config_* functions actually declared?

If you look closely in the file drivers/pci/pci.c, you will see the following code:

#define PCI_OP(rw,size,type) \
int pci_##rw##_config_##size (struct pci_dev *dev,
                              int pos, type value) \
{                                                  \
    int res;                                       \
    unsigned long flags;                           \
    if (PCI_##size##_BAD) return
       PCIBIOS_BAD_REGISTER_NUMBER;                \
    spin_lock_irqsave(&pci_lock, flags);           \
    res = dev->bus->ops->rw##_##size(dev, pos,
                                     value);       \
    spin_unlock_irqrestore(&pci_lock, flags);      \
    return res;                                    \
}

PCI_OP(read, byte, u8 *)
PCI_OP(read, word, u16 *)
PCI_OP(read, dword, u32 *)
PCI_OP(write, byte, u8)
PCI_OP(write, word, u16)
PCI_OP(write, dword, u32)