drm/rockchip: analogix_dp: allow to work without panel

When the DP output is routed to a external connector there is no
need for a fixed panel, as the panel may be detected via EDID on
the AUX channel. Allow to continue probing if no panel reference
is present.

Signed-off-by: Lucas Stach <[e-mail]>
Signed-off-by: Heiko Stuebner <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/rockchip/analogix_dp-rockchip.c

···
 		return -ENODEV;
 
 	ret = drm_of_find_panel_or_bridge(dev->of_node, 1, 0, &panel, NULL);
-	if (ret < 0)
+	if (ret < 0 && ret != -ENODEV)
 		return ret;
 
 	dp = devm_kzalloc(dev, sizeof(*dp), GFP_KERNEL);