[clang] [clang][SYCL] Implement address space attributes for SYCL (PR #200849)

[Erich Keane via cfe-commits]

erichkeane wrote:

> > I'm not sure that top-level type of a variable declaration is actually any better than the 'must be object pointer or reference'? Maybe 'must be pointer or reference', and let the function pointer check take care of clarifying it?
> 
> Do you mean `"'%0' attribute may only be applied to a pointer or reference"`

that SEEMS more readable to me? If you wanted to be extra kind, you could print the type you're applying it to in parens.

https://github.com/llvm/llvm-project/pull/200849