PCI: Add a stub for pci_ats_disabled()

Currently pci_ats_disabled() is only defined when CONFIG_PCI is enabled.
Since we're about to use the function in the Arm SMMUv3 driver, which
could be built with CONFIG_PCI disabled, add a definition of
pci_ats_disabled() for !CONFIG_PCI.
Acked-by: NBjorn Helgaas <bhelgaas@google.com>
Signed-off-by: NJean-Philippe Brucker <jean-philippe.brucker@arm.com>
Signed-off-by: NWill Deacon <will.deacon@arm.com>

include/linux/pci.h

@@ -1713,6 +1713,7 @@ static inline int pci_irqd_intx_xlate(struct irq_domain *d,
 static inline const struct pci_device_id *pci_match_id(const struct pci_device_id *ids,
 							 struct pci_dev *dev)
 { return NULL; }
+static inline bool pci_ats_disabled(void) { return true; }
 #endif /* CONFIG_PCI */
 
 #ifdef CONFIG_PCI_ATS