[#860] Add MH1903 platform description

[racerxdl]

Related issue

Fixes #860
Needs renode/renode-infrastructure#181

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[racerxdl]

Btw @PiotrZierhoffer you asked to add an buildable example here with a test platform so you can add it to CI to test and such. But I'm not sure where to add it. I didnt find any examples being built on this repo 🤔

(PR as a Draft until I do everything and update the body of the PR)