drm/amd/display: Enable legacy fast update for dcn301

Set up to enable legacy fast update.

Acked-by: Wayne Lin <wayne.lin@amd.com>
Signed-off-by: Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>
Tested-by: Daniel Wheeler <daniel.wheeler@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/display/dc/resource/dcn301/dcn301_resource.c

@@ -702,6 +702,7 @@ static const struct dc_debug_options debug_defaults_drv = {
 	.dmub_command_table = true,
 	.use_max_lb = false,
 	.exit_idle_opt_for_cursor_updates = true,
+	.enable_legacy_fast_update = true,
 	.using_dml2 = false,
 };