The two previously submitted bug fixes can actually be had as a side
effect of eliminating a bogus feature, the last use of which had
disappeared a while ago. Further cleanup then follows along the
lines of what had also been discussed in the context of the earlier
attempts.

1: simplify (and thus correct) pci_get_pdev{,_by_domain}()
2: fold pci_get_pdev{,_by_domain}()
3: bring pci_get_real_pdev() in line with pci_get_pdev()

Jan