[clang] [SPARC] use `divideCeil` to calculate register offset (PR #213739)

[Folkert de Vries via cfe-commits]

folkertdev wrote:

Yeah as expected that code early-returns and does not handle the padding, even with this change. I'll dig deeper, looks like this needs some refactoring. 

https://github.com/llvm/llvm-project/pull/213739