iommu: Introduce new 'struct iommu_device'

This struct represents one hardware iommu in the iommu core
code. For now it only has the iommu-ops associated with it,
but that will be extended soon.

The register/unregister interface is also added, as well as
making use of it in the Intel and AMD IOMMU drivers.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index c66c273..e6e8f5b 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -547,7 +547,7 @@ EXPORT_SYMBOL_GPL(intel_iommu_gfx_mapped);
 static DEFINE_SPINLOCK(device_domain_lock);
 static LIST_HEAD(device_domain_list);
 
-static const struct iommu_ops intel_iommu_ops;
+const struct iommu_ops intel_iommu_ops;
 
 static bool translation_pre_enabled(struct intel_iommu *iommu)
 {
@@ -5292,7 +5292,7 @@ struct intel_iommu *intel_svm_device_to_iommu(struct device *dev)
 }
 #endif /* CONFIG_INTEL_IOMMU_SVM */
 
-static const struct iommu_ops intel_iommu_ops = {
+const struct iommu_ops intel_iommu_ops = {
 	.capable	= intel_iommu_capable,
 	.domain_alloc	= intel_iommu_domain_alloc,
 	.domain_free	= intel_iommu_domain_free,