Integrate meta-seconorth-machine/bootscript-dtb-temp-overlay

Commit: seco-ne/yocto/layers/meta-seconorth-machine@2302d9d7

bootscript: Adapt load of temp grade overlays to support dtbo and dtb files

For the older kernels (5.10) the build of dtbo's is not supported in the kernel, so overlay.dtb is used here. This change allow to fallback to the old naming when search for the detected overlays.