[clang] [MSP430][Clang] Update list of MCUs (PR #91258)

[Marian Buschsieweke via cfe-commits]

maribu wrote:

Thx for the suggestion.

I interpreted `Target/MSP430` as relative to where the definitions are; was this correct?

My experience with LLVM is limited to using it, so I do not really know my way around :)

https://github.com/llvm/llvm-project/pull/91258