[clang] [lld] [llvm] [mlir] [NFC] Use more isa and isa_and_nonnull instead dyn_cast for predicates (PR #137393)

[Max Graey via cfe-commits]

MaxGraey wrote:

Hi, this is my first contribution in LLVM. I would like to know ho many approves needed and is there anything else needed on my side? Thanks!

https://github.com/llvm/llvm-project/pull/137393