[clang] [HLSL] Make cosh, exp, normalize overload tests stricter. NFC (PR #177507)

[Justin Bogner via cfe-commits]

https://github.com/bogner commented:

Similarly to https://github.com/llvm/llvm-project/pull/177495, I think the tests that just show we convert to float are spurious here.

https://github.com/llvm/llvm-project/pull/177507