SPICE Model refactoring

[christoph-weiser]

SPICE Model refactoring

Is there any intent to refactor the PDK? I suggest to make this a priority before tinkering more with the PDK itself because I observed the following issues.

• The delta between the ngspice and xyce model is very big, even though it turns out there is only small differences.
• There is extensive whitespace in the xyce model for no appearant reason.
• There is inconsistency between the two models, where it seems like it should not.

I tried to refactor both xyce and ngspice models in the fork that created from this repository (link)

[atorkmabrains]

@christoph-weiser Please check here:
https://github.com/efabless/globalfoundries-pdk-libs-gf180mcu_fd_pr/tree/main

@christoph-weiser I advise that you create a PR a the link above for me to review.