dto: Refactor fixup generation
To use labels of the overlayed device tree we need to use fixups. This is somewhat clumsy as we have to write the fixup in a special node not related to the currently edited node. Furthermore changing the fixup node may change the offset of the currently edited node.
Add a function create_property_fixup to do exactly that. It also returns the possibly changed node offset of the changed node.
This renders the generate_tagret_string unnecessary and it can be removed.
We might want to use this for the dto_touch.c as well thus export the function in a header.
BCS 746-000277