[clang] [X86][AVX10.2] Add comments for the avx10_2convertintrin.h file (PR #120766)

[Phoebe Wang via cfe-commits]

phoebewang wrote:

We cannot let clang-format to format it. Maybe use `clang-format off` to turn it off.

https://github.com/llvm/llvm-project/pull/120766