[llvm] [DAG] Reducing instructions by better legalization handling of AVGFLOORU for illegal data types (PR #99913)

[Simon Pilgrim via llvm-commits]

RKSimon wrote:

No, if you run `ninja check-llvm-codegen` you should see that you need to regenerate:
```
LLVM :: CodeGen/RISCV/avgflooru.ll
LLVM :: CodeGen/X86/avgflooru-scalar.ll
```

https://github.com/llvm/llvm-project/pull/99913