[clang] [Sparc][clang] Match GCC's SPARC V8 vector argument passing (PR #222254)

[Folkert de Vries via cfe-commits]

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folkertdev wrote:

I'd expect (not in this file but somewhere) some tests using standard (so, non-variadic) calls too. The change in `SparcV8ABIInfo::classifyArgumentType` would apply to them too so best to lock that in.

https://github.com/llvm/llvm-project/pull/222254