[clang] [CMake] Link only the MLIR dialects ClangIR uses (PR #221616)

[Mehdi Amini via cfe-commits]

https://github.com/joker-eph approved this pull request.

Thanks! I've been doing the same for Flang and was about to do this for CIR as well, your beat me to it :) 

https://github.com/llvm/llvm-project/pull/221616