iommu/vt-d: Fix page request descriptor size

Intel VT-d might support PRS (Page Reqest Support) when it's
running in the scalable mode. Each page request descriptor
occupies 32 bytes and is 32-bytes aligned. The page request
descriptor offset mask should be 32-bytes aligned.

Fixes: 5b438f4b ("iommu/vt-d: Support page request in scalable mode")
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/intel-svm.c

@@ -531,7 +531,7 @@ struct page_req_dsc {
 	u64 priv_data[2];
 };
 
-#define PRQ_RING_MASK ((0x1000 << PRQ_ORDER) - 0x10)
+#define PRQ_RING_MASK	((0x1000 << PRQ_ORDER) - 0x20)
 
 static bool access_error(struct vm_area_struct *vma, struct page_req_dsc *req)
 {