[llvm] [AArch64][GISel] Assign registers into FPR if they feed into FP instructions indirectly via PHI (PR #94618)

[via llvm-commits]

Him188 wrote:

> `%4` is used by a floating operation (G_FCMP)?!?

`%4` is copied into `%29` then used by G_FCMP, isn't it?

https://github.com/llvm/llvm-project/pull/94618