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/nvidia-agp.c

@@ -225,7 +225,7 @@ static int nvidia_insert_memory(struct agp_memory *mem, off_t pg_start, int type
 	}
 	for (i = 0, j = pg_start; i < mem->page_count; i++, j++) {
 		writel(agp_bridge->driver->mask_memory(agp_bridge,
-			mem->pages[i], mask_type),
+			       phys_to_gart(page_to_phys(mem->pages[i])), mask_type),
 			agp_bridge->gatt_table+nvidia_private.pg_offset+j);
 	}