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