[clang] [AArch64] Diagnose more functions when FP not enabled (PR #90832)

[Eli Friedman via cfe-commits]

https://github.com/efriedma-quic commented:

I'm a little unhappy with the duplicated logic between checkFunctionCallABI and checkFunctionABI; is there some way we can unify?  Even if it doesn't actually reduce the code duplication very much, it would be helpful to clarify that both paths are checking for the same thing.

https://github.com/llvm/llvm-project/pull/90832