[sony-amami] backlight workaround for weston is broken

Created by: ollieparanoid

@ata2001 reported in the chat, that fb-workaround.sh doesn't work anymore since weston doesn't run as root anymore. Because it depended on autologin as root.

My proposed workaround was using an OpenRC service instead of autologin (which will go away when we have a display manager anyway).