drm/vc4: hdmi: do not return negative values from .get_modes()

The .get_modes() hooks aren't supposed to return negative error
codes. Return 0 for no modes, whatever the reason.

Cc: Maxime Ripard <mripard@kernel.org>
Cc: stable@vger.kernel.org
Acked-by: Maxime Ripard <mripard@kernel.org>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/dcda6d4003e2c6192987916b35c7304732800e08.1709913674.git.jani.nikula@intel.comSigned-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/vc4/vc4_hdmi.c

@@ -509,7 +509,7 @@ static int vc4_hdmi_connector_get_modes(struct drm_connector *connector)
 	edid = drm_get_edid(connector, vc4_hdmi->ddc);
 	cec_s_phys_addr_from_edid(vc4_hdmi->cec_adap, edid);
 	if (!edid)
-		return -ENODEV;
+		return 0;
 
 	drm_connector_update_edid_property(connector, edid);
 	ret = drm_add_edid_modes(connector, edid);