drm/ttm: drop ttm->dummy_read_page

Only used by the AGP backend and there it can be easily accessed using
ttm->bdev->glob.

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Michel Dänzer <michel.daenzer@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/bochs/bochs_mm.c

@@ -178,8 +178,7 @@ static struct ttm_backend_func bochs_tt_backend_func = {
 
 static struct ttm_tt *bochs_ttm_tt_create(struct ttm_bo_device *bdev,
 					  unsigned long size,
-					  uint32_t page_flags,
-					  struct page *dummy_read_page)
+					  uint32_t page_flags)
 {
 	struct ttm_tt *tt;
 
@@ -187,7 +186,7 @@ static struct ttm_tt *bochs_ttm_tt_create(struct ttm_bo_device *bdev,
 	if (tt == NULL)
 		return NULL;
 	tt->func = &bochs_tt_backend_func;
-	if (ttm_tt_init(tt, bdev, size, page_flags, dummy_read_page)) {
+	if (ttm_tt_init(tt, bdev, size, page_flags)) {
 		kfree(tt);
 		return NULL;
 	}