[llvm] [RISCV] Fold subtraction if above threshold to Zbb `minu` (PR #134235)

[Piotr Fusik via llvm-commits]

pfusik wrote:

Build failed with:

```
# | error: 'expected-note' diagnostics expected but not seen: 
# |   File C:\ws\src\clang\test\CXX\temp\temp.arg\temp.arg.type\p2.cpp Line 17 (directive at C:\ws\src\clang\test\CXX\temp\temp.arg\temp.arg.type\p2.cpp:18): unnamed type used in template argument was declared here
```

I don't believe this is caused by my change.

https://github.com/llvm/llvm-project/pull/134235