Integrate meta-guf-machine/remove-nallino-uboot-recipes

Commit: https://gitlab.com/SECO-Northern-Europe/yocto/layers/meta-guf-machine/-/commit/c3a5c51418649a0f3b36eaee2769c8ffeea27cec

imx6ullguf: Remove u-boot recipes and config for Nallino, not used anymore

We switched to fngboot for Nallino, so we don't need the u-boot receipes anymore. The imx8 derivates are using u-boot-imx with other recipes.