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/include/asm/amd_iommu_proto.h b/arch/x86/include/asm/amd_iommu_proto.h
index 2566e26..4d817f9 100644
--- a/arch/x86/include/asm/amd_iommu_proto.h
+++ b/arch/x86/include/asm/amd_iommu_proto.h
@@ -30,6 +30,7 @@
 extern void amd_iommu_reset_cmd_buffer(struct amd_iommu *iommu);
 extern int amd_iommu_init_devices(void);
 extern void amd_iommu_uninit_devices(void);
+extern void amd_iommu_init_notifier(void);
 #ifndef CONFIG_AMD_IOMMU_STATS
 
 static inline void amd_iommu_stats_init(void) { }