PCI: Add pci_dev_flag for ACS enable quirks

Quirks that enable ACS-compatible functionality on a device need some way
to track whether a given device has been enabled.  Rather than create new
data structures for this, allocate one of the pci_dev_flags to indicate
this setup.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

include/linux/pci.h

@@ -170,6 +170,8 @@ enum pci_dev_flags {
 	PCI_DEV_FLAGS_NO_D3 = (__force pci_dev_flags_t) 2,
 	/* Provide indication device is assigned by a Virtual Machine Manager */
 	PCI_DEV_FLAGS_ASSIGNED = (__force pci_dev_flags_t) 4,
+	/* Flag for quirk use to store if quirk-specific ACS is enabled */
+	PCI_DEV_FLAGS_ACS_ENABLED_QUIRK = (__force pci_dev_flags_t) 8,
 };
 
 enum pci_irq_reroute_variant {