PCI: Remove unused pci_lost_interrupt()

388c8c16 ("PCI: add routines for debugging and handling lost
interrupts") added pci_lost_interrupt() that apparently never has had a
single user.  Remove it.

Link: https://lore.kernel.org/r/e328d059-3068-6a40-28df-f81f616d15a0@gmail.com


Signed-off-by: Heiner Kallweit <hkallweit1@gmail.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>