drm/msm: fix opencoded use of drm_panel_*

Use the function drm_panel_get_modes().
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Reviewed-by: Emil Velikov <emil.velikov@collabora.com>
Cc: Alexios Zavras <alexios.zavras@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Allison Randal <allison@lohutok.net>
Cc: Enrico Weigelt <info@metux.net>
Link: https://patchwork.freedesktop.org/patch/msgid/20190804201637.1240-7-sam@ravnborg.org

drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c

@@ -53,7 +53,7 @@ static int mdp4_lvds_connector_get_modes(struct drm_connector *connector)
 	if (panel) {
 		drm_panel_attach(panel, connector);
 
-		ret = panel->funcs->get_modes(panel);
+		ret = drm_panel_get_modes(panel);
 
 		drm_panel_detach(panel);
 	}