x86/amd-iommu: Fix PCI hotplug with passthrough mode

The device change notifier is initialized in the dma_ops
initialization path. But this path is never executed for
iommu=pt. Move the notifier initialization to IOMMU hardware
init code to fix this.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
diff --git a/arch/x86/kernel/amd_iommu.c b/arch/x86/kernel/amd_iommu.c
index 450dd6a..a831850 100644
--- a/arch/x86/kernel/amd_iommu.c
+++ b/arch/x86/kernel/amd_iommu.c
@@ -1624,6 +1624,11 @@
 	.notifier_call = device_change_notifier,
 };
 
+void amd_iommu_init_notifier(void)
+{
+	bus_register_notifier(&pci_bus_type, &device_nb);
+}
+
 /*****************************************************************************
  *
  * The next functions belong to the dma_ops mapping/unmapping code.
@@ -2250,8 +2255,6 @@
 
 	register_iommu(&amd_iommu_ops);
 
-	bus_register_notifier(&pci_bus_type, &device_nb);
-
 	amd_iommu_stats_init();
 
 	return 0;