Update Wayland notes on the Embedded Linux page

Qt Wayland is now part of the 5.4 release.

Change-Id: I7153d6bce72805a85b0205acdcae9bfe826b62fa
Reviewed-by: Louai Al-Khanji <louai.al-khanji@theqtcompany.com>
Reviewed-by: Robin Burchell <robin.burchell@viroteck.net>