agp: kill phys_to_gart() and gart_to_phys()

There seems to be no reason for these -- they're a 1:1 mapping on all
platforms.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/drivers/char/agp/backend.c b/drivers/char/agp/backend.c
index 343f102..ad87753 100644
--- a/drivers/char/agp/backend.c
+++ b/drivers/char/agp/backend.c
@@ -159,7 +159,7 @@
 				goto err_out_nounmap;
 			}
 		} else {
-			bridge->scratch_page_dma = phys_to_gart(page_to_phys(page));
+			bridge->scratch_page_dma = page_to_phys(page);
 		}
 
 		bridge->scratch_page = bridge->driver->mask_memory(bridge,