[llvm] [ScalarizeMaskedMemIntr] Don't use a scalar mask on GPUs (PR #104842)

[Krzysztof Drewniak via llvm-commits]

krzysz00 wrote:

@jayfoad I don't have any examples of better codegen for CPUs - and I'm not the person who wrote that initial comment, maybe they know.

But I've definitely seen a bunch of `v_and`s in the ISA that didn't need to be there

https://github.com/llvm/llvm-project/pull/104842