[clang] [llvm] [LangRef] Describe semantic impact of non-temporal memory access. (PR #178264)

[Aaron Ballman via cfe-commits]

https://github.com/AaronBallman approved this pull request.

Clang bits LGTM, but someone else should approve the LLVM bits. Thank you for the improved docs!

https://github.com/llvm/llvm-project/pull/178264