Stop caching the Invalidate Queue Depth in struct pci_dev.
pci_ats_queue_depth() is typically called only once per device, and it
returns a fixed value per-device, so callers who need the value frequently
can cache it themselves.
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Reviewed-by: NJoerg Roedel <jroedel@suse.de>