drm/imx/ipuv3: 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: Philipp Zabel <p.zabel@pengutronix.de>
Cc: stable@vger.kernel.org
Acked-by: Philipp Zabel <p.zabel@pengutronix.de>
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
Link: https://patchwork.freedesktop.org/patch/msgid/311f6eec96d47949b16a670529f4d89fcd97aefa.1709913674.git.jani.nikula@intel.comSigned-off-by: Jani Nikula <jani.nikula@intel.com>

drivers/gpu/drm/imx/ipuv3/parallel-display.c

@@ -72,14 +72,14 @@ static int imx_pd_connector_get_modes(struct drm_connector *connector)
 		int ret;
 
 		if (!mode)
-			return -EINVAL;
+			return 0;
 
 		ret = of_get_drm_display_mode(np, &imxpd->mode,
 					      &imxpd->bus_flags,
 					      OF_USE_NATIVE_MODE);
 		if (ret) {
 			drm_mode_destroy(connector->dev, mode);
-			return ret;
+			return 0;
 		}
 
 		drm_mode_copy(mode, &imxpd->mode);