cleanup hardcoded path in makefiles

[proppy]

There seems to be quite a few hardcoded path in various makefiles:
https://github.com/efabless/caravel_mgmt_soc_litex/search?q=Users%2Fjeffdi

I'm not sure if those interfer with the default build process, but it'd be nice to clean them up.

[azwefabless]

Files should be removed. Generically this is not a blocker for caravel or tapeout of next device. The auto gnerated file is unused bu will queue for fix.