libweston-desktop: Drop (wrongly named) new_buffer in committed

Instead we store the buffer move and just use it when the signal is
fired.

Signed-off-by: Quentin Glidic <sardemff7+git@sardemff7.net>
Reviewed-by: Jonas Ådahl <jadahl@gmail.com>
diff --git a/libweston-desktop/xwayland.c b/libweston-desktop/xwayland.c
index 7362a72..6c63483 100644
--- a/libweston-desktop/xwayland.c
+++ b/libweston-desktop/xwayland.c
@@ -112,7 +112,7 @@
 
 static void
 weston_desktop_xwayland_surface_committed(struct weston_desktop_surface *dsurface,
-					  void *user_data, bool new_buffer,
+					  void *user_data,
 					  int32_t sx, int32_t sy)
 {
 	struct weston_desktop_xwayland_surface *surface = user_data;