xcursor: fix duplicate cursor check check in load_callback()

wlr_xcursor_theme_get_cursor() now does some fallback logic. We
don't want that for checking whether a cursor has already been
loaded.

Fixes: dbedcdb418 ("xcursor: add fallbacks for legacy names")
Closes: https://gitlab.freedesktop.org/wlroots/wlroots/-/issues/3783

xcursor/wlr_xcursor.c

@@ -170,10 +170,13 @@ static struct wlr_xcursor *xcursor_create_from_xcursor_images(
 	return cursor;
 }
 
+static struct wlr_xcursor *xcursor_theme_get_cursor(struct wlr_xcursor_theme *theme,
+	const char *name);
+
 static void load_callback(struct xcursor_images *images, void *data) {
 	struct wlr_xcursor_theme *theme = data;
 
-	if (wlr_xcursor_theme_get_cursor(theme, images->name)) {
+	if (xcursor_theme_get_cursor(theme, images->name)) {
 		xcursor_images_destroy(images);
 		return;
 	}