pci: Rename pci_xbox_blacklisted() as pci_xbox_ignore_device()

In order to use inclusive terminology, rename pci_xbox_blacklisted()
as pci_xbox_ignore_device(), and remove an obvious comment.

Suggested-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk>