LinuxKPI: pci re-add pci_free_irq_vectors()

Re-add pci_free_irq_vectors() accidentally removed in
d4a4960c6559caa890af0901a21296e75b961210 and now needed by drm-kmod v5.5.

Reported by: wulf
Sponsored by: The FreeBSD Foundation
MFC after: 3 days
X-MFC with: d4a4960c6559caa890af0901a21296e75b961210