iommu/amd: Remove unused struct member

Commit c805b428 ("iommu/amd: Remove amd_iommu_pd_list") removes
the global list for the allocated protection domains. The
corresponding member 'list' of the protection_domain struct is
not used anymore, so it can be removed.
Signed-off-by: Adrian Huang <ahuang12@lenovo.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/amd_iommu_types.h

@@ -463,7 +463,6 @@ struct amd_irte_ops;
  * independent of their use.
  */
 struct protection_domain {
-	struct list_head list;  /* for list of all protection domains */
 	struct list_head dev_list; /* List of all devices in this domain */
 	struct iommu_domain domain; /* generic domain handle used by
 				       iommu core code */