swupdate: Add platform settings for SWUpdate and remove separate image recipes
Instead of creating platform-specific recipes for SWUpdate images we want to use the default image-ktn* recipes and only append the platform-specific configuration.
The seperate SWUpdate image recipes are not required anymore and can be removed.
This MR depends on meta-ktn!43 (merged) and build-ktn-imx!66 (merged).
Edited by Eberhard Stoll