[llvm] [NFC][MC] Use `StringRef` for Modifier in Inst/Asm Printers (PR #135403)

[Sergei Barannikov via llvm-commits]

https://github.com/s-barannikov approved this pull request.

Thanks,
LGTM with MSP430 fixed (failing pre-commit checks)


https://github.com/llvm/llvm-project/pull/135403