backend-drm: don't try to disable planes on session deactivation

This uses the legacy DRM API it incomplete and no longer works anyways.
At this point, weston is no longer DRM master, so these calls fail with
"Permission denied".

So just remove the corresponding code.

Signed-off-by: Michael Olbrich <m.olbrich@pengutronix.de>

libweston/backend-drm/drm.c

@@ -2686,9 +2686,7 @@ session_notify(struct wl_listener *listener, void *data)
 	struct weston_compositor *compositor = data;
 	struct drm_backend *b = to_drm_backend(compositor);
 	struct drm_device *device = b->drm;
-	struct drm_plane *plane;
 	struct drm_output *output;
-	struct drm_crtc *crtc;
 
 	if (compositor->session_active) {
 		weston_log("activating session\n");
@@ -2710,24 +2708,8 @@ session_notify(struct wl_listener *listener, void *data)
 		 * back, we schedule a repaint, which will process
 		 * pending frame callbacks. */
 
-		wl_list_for_each(output, &compositor->output_list, base.link) {
+		wl_list_for_each(output, &compositor->output_list, base.link)
-			crtc = output->crtc;
 			output->base.repaint_needed = false;
-			if (output->cursor_plane)
-				drmModeSetCursor(device->drm.fd, crtc->crtc_id,
-						 0, 0, 0);
-		}
-
-		output = container_of(compositor->output_list.next,
-				      struct drm_output, base.link);
-		crtc = output->crtc;
-
-		wl_list_for_each(plane, &device->plane_list, link) {
-			if (plane->type != WDRM_PLANE_TYPE_OVERLAY)
-				continue;
-			drmModeSetPlane(device->drm.fd, plane->plane_id, crtc->crtc_id,
-					0, 0, 0, 0, 0, 0, 0, 0, 0, 0);
-		}
 	}
 }