agp: Switch mask_memory() method to take address argument again, not page

In commit 07613ba2 ("agp: switch AGP to use page array instead of
unsigned long array") we switched the mask_memory() method to take a
'struct page *' instead of an address. This is painful, because in some
cases it has to be an IOMMU-mapped virtual bus address (in fact,
shouldn't it _always_ be a dma_addr_t returned from pci_map_xxx(), and
we just happen to get lucky most of the time?)

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

drivers/char/agp/backend.c

@@ -150,8 +150,8 @@ static int agp_backend_initialize(struct agp_bridge_data *bridge)
 		}
 
 		bridge->scratch_page_real = phys_to_gart(page_to_phys(page));
-		bridge->scratch_page =
-		    bridge->driver->mask_memory(bridge, page, 0);
+		bridge->scratch_page = bridge->driver->mask_memory(bridge,
+					   phys_to_gart(page_to_phys(page)), 0);
 	}
 
 	size_value = bridge->driver->fetch_size();