iommu/vt-d: Fix a variable set but not used

The commit "iommu/vt-d: Delegate the dma domain to upper layer" left an
unused variable,

drivers/iommu/intel-iommu.c: In function 'disable_dmar_iommu':
drivers/iommu/intel-iommu.c:1652:23: warning: variable 'domain' set but
not used [-Wunused-but-set-variable]
Signed-off-by: Qian Cai <cai@lca.pw>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-iommu.c

@@ -1649,16 +1649,12 @@ static void disable_dmar_iommu(struct intel_iommu *iommu)
 
 	spin_lock_irqsave(&device_domain_lock, flags);
 	list_for_each_entry_safe(info, tmp, &device_domain_list, global) {
-		struct dmar_domain *domain;
-
 		if (info->iommu != iommu)
 			continue;
 
 		if (!info->dev || !info->domain)
 			continue;
 
-		domain = info->domain;
-
 		__dmar_remove_one_dev_info(info);
 	}
 	spin_unlock_irqrestore(&device_domain_lock, flags);