[clang] [clang][Sema] Bad register variable type error should point to the type (PR #110239)

[David Spickett via cfe-commits]

DavidSpickett wrote:

I also think that "bad" is a confusing word to use here, "unsupported" would be better but I will address that in a follow up PR.

https://github.com/llvm/llvm-project/pull/110239