Integrate meta-seconorth-machine/add-devicetree-links-again

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Commit: seco-ne/yocto/layers/meta-seconorth-machine@3b1155bf

kernel:dtb: Create devicetree links named like the original dtb names in deploy folder

In the rootfs/boot folder the devicetrees are named like the kernel
sources, in the deploy folder they get a long postfix. For CI deploy
step and the usage of the dtb name during installation the original
names are needed in the deploy folder too.
This patch takes a snippet from the kernel-devicetree.bbclass to enable
it again, because the yocto way to enable it, also brings links to the
kernel image inside the rootfs, which does not work for us, because of
the fat filessystem on the boot partition.

BCS 746-001026