Fix Steam Deck Dual Boot not Booting after Steam OS Update (3.4)

Here is a quick workaround and a quick fix to get you back up and running without losing any data or having to download, install, re-image or otherwise make a lot of work to get things back to normal if your Steam Deck stopped booting or now only boots to Windows after an update.

This is affecting the most people after the most recent SteamOS 3.4 update as it changed the EFI boot loader settings.

We could manually fix those things, but this is the easiest solution that I could come up with to share, not everybody wants to get super details with terminal commands and system investigation.