Integrate meta-seconorth-mtk/cleanup_dtbo

Commit: https://git.seco.com/seco-ne/yocto/layers/meta-seconorth-mtk/-/commit/4717020e07e6db57ecd45d0658d6d9d0f59b0058

recipes-kernel:dtbo:b79: move hdmi and dsi node to dtbo

As there is only one "standard" device tree file defined in machine.conf, it will include only module-specific things and all external stuff should be moved to overlays

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Commit: https://git.seco.com/seco-ne/yocto/layers/meta-seconorth-mtk/-/commit/83f689a074cd7aa4ac4fd8eeceda5c7a137de355

recipes-kernel:dtbo: Cleanup dtbo directory

All these dtbo files are not needed in machine layer, as they are pulled from meta-mediatek-bsp layer. Only seco-specific files should stay in this layer.