[clang] [clang] Fix crash in code with StmtExpr and atomic char load in Expr::EvaluateAsRValue. (PR #106751)

[via cfe-commits]

c8ef wrote:

I'm curious about why Clang emits atomic-to-non-atomic and non-atomic-to-atomic conversions when the type of the expression is atomic and the input is also atomic. 
(I'm not very familiar with C++ expression rules, so I may have missed something in the standards.)

https://github.com/llvm/llvm-project/pull/106751