[llvm] Add support for x87 registers on GISel register selection (PR #83528)

[Thorsten Schütt via llvm-commits]

tschuett wrote:

```
This is required because with SSE enabled, x86 doesn't use fp stack and instead uses AVX registers.
```
Did you mean SSE registers?

https://github.com/llvm/llvm-project/pull/83528