drm: cleanup use of Linux list handling macros

This makes the drms use of the list handling macros a lot cleaner
and more along the lines of how they should be used and uses them
in some more places.

Signed-off-by: Dave Airlie <airlied@linux.ie>
diff --git a/drivers/char/drm/mga_dma.c b/drivers/char/drm/mga_dma.c
index c2a4bac..5781a8d 100644
--- a/drivers/char/drm/mga_dma.c
+++ b/drivers/char/drm/mga_dma.c
@@ -551,7 +551,7 @@
 		drm_map_list_t *_entry;
 		unsigned long agp_token = 0;
 		
-		list_for_each_entry(_entry, &dev->maplist->head, head) {
+		list_for_each_entry(_entry, &dev->maplist, head) {
 			if (_entry->map == dev->agp_buffer_map)
 				agp_token = _entry->user_token;
 		}