add support for GF180MCU pdk

[kassemmkk]

Originally created by proppy on 2022-11-23T03:27:38Z

So that analog projects can be submitted to GF-MPW1+

[kassemmkk]

Comment originally by proppy on 2023-02-11T05:56:22Z

RTimothyEdwards mentioned in https://open-source-silicon.slack.com/archives/C03R1GRP9LG/p1675914768575299 mentioned that the following things could be done:

• replacing 11 GPIO along the top and sides with analog pads
• extracting the verilog for the padframe and toplevel
• define where the user analog project area is

Some of that work started to happen in efabless/caravel-gf180mcu@1c6f473.