Integrate meta-guf-machine/imx8m-plus

Commit: https://gitlab.com/garz-fricke/yocto/layers/meta-guf-machine/-/commit/990d957b69d62ede3a13157d83a8901bb6d07ce6

imx8mpguf:Add new machine for imx8m plus variant

Add machine conf. Adapt u-boot branch for new machine. Adapt imxmkimage branch for new machine. Adapt kernel receipe.

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Commit: https://gitlab.com/garz-fricke/yocto/layers/meta-guf-machine/-/commit/3a7673b4a59b20b92b4143738ea2e6184e222d67

imx8mguf:kernel:defconfig: Merge changes from imx_v8_defconfig used by kuk.

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Commit: https://gitlab.com/garz-fricke/yocto/layers/meta-guf-machine/-/commit/38feda1dd95eae5ac43267b9221c6e441977c04a

imx8mguf:kernel:defconfig: Save a 'savedefconfig' defconfig without changes.