drm/ttm: add io_mem_pfn callback

This allows the driver to handle io_mem mappings on their own.

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

drivers/gpu/drm/qxl/qxl_ttm.c

@@ -393,6 +393,7 @@ 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,
 };