drm/qxl: remove the default io_mem_pfn set

The default interface situation has been taken into the framework, so
remove the default set of each module.
Signed-off-by: Tan Xiaojun <tanxiaojun@huawei.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/qxl/qxl_ttm.c

@@ -388,7 +388,6 @@ static struct ttm_bo_driver qxl_bo_driver = {
 	.verify_access = &qxl_verify_access,
 	.io_mem_reserve = &qxl_ttm_io_mem_reserve,
 	.io_mem_free = &qxl_ttm_io_mem_free,
-	.io_mem_pfn = ttm_bo_default_io_mem_pfn,
 	.move_notify = &qxl_bo_move_notify,
 };