iommu: Implement DOMAIN_ATTR_PAGING attribute

This attribute of a domain can be queried to find out if the
domain supports setting up page-tables using the iommu_map()
and iommu_unmap() functions.

Signed-off-by: Joerg Roedel <joro@8bytes.org>
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 4e6d6f8..0e0e5f2 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -869,6 +869,7 @@
 			  enum iommu_attr attr, void *data)
 {
 	struct iommu_domain_geometry *geometry;
+	bool *paging;
 	int ret = 0;
 
 	switch (attr) {
@@ -877,6 +878,10 @@
 		*geometry = domain->geometry;
 
 		break;
+	case DOMAIN_ATTR_PAGING:
+		paging  = data;
+		*paging = (domain->ops->pgsize_bitmap != 0UL);
+		break;
 	default:
 		if (!domain->ops->domain_get_attr)
 			return -EINVAL;