irqchip/MSI: Use irq_domain_update_bus_token instead of an open coded access

Now that we have irq_domain_update_bus_token(), switch everyone over
to it. The debugfs code thanks you for your continued support.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
diff --git a/drivers/pci/msi.c b/drivers/pci/msi.c
index ba44fdf..fbad5dc 100644
--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1463,7 +1463,7 @@ struct irq_domain *pci_msi_create_irq_domain(struct fwnode_handle *fwnode,
 	if (!domain)
 		return NULL;
 
-	domain->bus_token = DOMAIN_BUS_PCI_MSI;
+	irq_domain_update_bus_token(domain, DOMAIN_BUS_PCI_MSI);
 	return domain;
 }
 EXPORT_SYMBOL_GPL(pci_msi_create_irq_domain);