drm/panel: drop return code from drm_panel_detach()

There are no errors that can be reported by this function,
so drop the return code.
Fix the only bridge driver that checked the return result.

Signed-off-by: Sam Ravnborg <[e-mail]>
Reviewed-by: Laurent Pinchart <[e-mail]>
Reviewed-by: Emil Velikov <[e-mail]>
Cc: Thierry Reding <[e-mail]>
Cc: Sam Ravnborg <[e-mail]>
Cc: Maarten Lankhorst <[e-mail]>
Cc: Maxime Ripard <[e-mail]>
Cc: Sean Paul <[e-mail]>
Cc: David Airlie <[e-mail]>
Cc: Daniel Vetter <[e-mail]>
Cc: Laurent Pinchart <[e-mail]>
Cc: Andrzej Hajda <[e-mail]>
Cc: Gwan-gyeong Mun <[e-mail]>
Cc: Thomas Gleixner <[e-mail]>
Cc: Linus Walleij <[e-mail]>
Link: https://patchwork.freedesktop.org/patch/msgid/[e-mail]

drivers/gpu/drm/bridge/analogix/analogix_dp_core.c

···
 	if (dp->plat_data->panel) {
 		if (drm_panel_unprepare(dp->plat_data->panel))
 			DRM_ERROR("failed to turnoff the panel\n");
-		if (drm_panel_detach(dp->plat_data->panel))
-			DRM_ERROR("failed to detach the panel\n");
+		drm_panel_detach(dp->plat_data->panel);
 	}
 
 	drm_dp_aux_unregister(&dp->aux);

drivers/gpu/drm/drm_panel.c

···
  *
  * This function should not be called by the panel device itself. It
  * is only for the drm device that called drm_panel_attach().
- *
- * Return: 0 on success or a negative error code on failure.
  */
-int drm_panel_detach(struct drm_panel *panel)
+void drm_panel_detach(struct drm_panel *panel)
 {
 	panel->connector = NULL;
 	panel->drm = NULL;
-
-	return 0;
 }
 EXPORT_SYMBOL(drm_panel_detach);
 

include/drm/drm_panel.h

···
 void drm_panel_remove(struct drm_panel *panel);
 
 int drm_panel_attach(struct drm_panel *panel, struct drm_connector *connector);
-int drm_panel_detach(struct drm_panel *panel);
+void drm_panel_detach(struct drm_panel *panel);
 
 int drm_panel_prepare(struct drm_panel *panel);
 int drm_panel_unprepare(struct drm_panel *panel);