[clang] [libclc] Clang: Deprecate float support from __builtin_elementwise_max (PR #180885)

[Matt Arsenault via cfe-commits]

arsenm wrote:

> This might not have been noticed because, unlike the `__builtin_fmax` handling, Clang's `__builtin_elementwise_max` doesn't set the `nsz` flag so the backend never gets the message that it can ignore the sign of zero on operands, but I'm pretty sure that Clang's documentation for `__builtin_elementwise_max` is saying that the sign of zero may be ignored.
> 

If you really really want that, that should be a distinct elementwise fmin/fmax. 

Alternatively we should round out the math pragmas to have nsz 



https://github.com/llvm/llvm-project/pull/180885