iommu/amd: Use dev_data->domain in get_domain()

Using the cached value is much more efficient than calling
into the IOMMU core code.
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/amd_iommu.c

@@ -2215,16 +2215,11 @@ static void queue_add(struct dma_ops_domain *dma_dom,
 static struct protection_domain *get_domain(struct device *dev)
 {
 	struct protection_domain *domain;
-	struct iommu_domain *io_domain;
 
 	if (!check_device(dev))
 		return ERR_PTR(-EINVAL);
 
-	io_domain = iommu_get_domain_for_dev(dev);
-	if (!io_domain)
-		return NULL;
-
-	domain = to_pdomain(io_domain);
+	domain = get_dev_data(dev)->domain;
 	if (!dma_ops_domain(domain))
 		return ERR_PTR(-EBUSY);