iommu/vt-d: Don't register bus-notifier under dmar_global_lock

The notifier function will take the dmar_global_lock too, so
lockdep complains about inverse locking order when the
notifier is registered under the dmar_global_lock.

Reported-by: Jan Kiszka <jan.kiszka@siemens.com>
Fixes: 59ce0515cdaf ('iommu/vt-d: Update DRHD/RMRR/ATSR device scope caches when PCI hotplug happens')
Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git a/include/linux/dmar.h b/include/linux/dmar.h
index e8ffba1..e2433bc 100644
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -112,6 +112,7 @@ static inline bool dmar_rcu_check(void)
 
 extern int dmar_table_init(void);
 extern int dmar_dev_scope_init(void);
+extern void dmar_register_bus_notifier(void);
 extern int dmar_parse_dev_scope(void *start, void *end, int *cnt,
 				struct dmar_dev_scope **devices, u16 segment);
 extern void *dmar_alloc_dev_scope(void *start, void *end, int *cnt);