adapt setup_env script to Vitis

[catkira]

@rgetz the newer Vivado/Vitis versions use /tools/Xilinx as prefix. I think the setup_env script should support the old /opt/Xilinx and the new /tools/Xilinx for a transition period. Will You update this script or should users setup up their environment manually as described in README.md ?

[catkira]

I have created a setup_env script for Vivado/Vitis 2022.1 in this PR #68

I think it makes sense to have it in a separate script, because the procedure is quite different compared to older Xilinx tools versions.