Draft: WIP update fwk Vitis integration

Some changes to fwk were necessary in another project (lisa_pm_adc) for its MicroBlaze software.

These require a few updates in this project.

See fpgafw/fwk!61.

This only affects the software that is built for the ARM Cortex-A53. When comparing the ELF files generated by this project before and after this change, all section headers are identical except some debug sections. This gives me confidence that the binaries are equivalent.

Draft until the fwk change is merged.