wayland: Perform a round trip when maximizing and restoring windows

Perform a round trip when maximizing and restoring windows so the changes have already taken effect when the associated functions return.

(cherry picked from commit 50f2eb7d41fbba7c82630e55ead4ecf9c32f4c69)

src/video/wayland/SDL_waylandwindow.c

@@ -1781,7 +1781,7 @@ void Wayland_RestoreWindow(_THIS, SDL_Window *window)
             xdg_toplevel_unset_maximized(wind->shell_surface.xdg.roleobj.toplevel);
         }
 
-    WAYLAND_wl_display_flush(viddata->display);
+    WAYLAND_wl_display_roundtrip(viddata->display);
 }
 
 void Wayland_SetWindowBordered(_THIS, SDL_Window *window, SDL_bool bordered)
@@ -1860,7 +1860,7 @@ void Wayland_MaximizeWindow(_THIS, SDL_Window *window)
         xdg_toplevel_set_maximized(wind->shell_surface.xdg.roleobj.toplevel);
     }
 
-    WAYLAND_wl_display_flush(viddata->display);
+    WAYLAND_wl_display_roundtrip(viddata->display);
 }
 
 void Wayland_MinimizeWindow(_THIS, SDL_Window *window)