[llvm] [RISCV] Porting hasAllNBitUsers to RISCV GISel for instruction select (PR #125795)

[Luke Quinn via llvm-commits]

lquinn2015 wrote:

I had a major git issue where my previous PR would not sync for whatever reason 

@michaelmaitland  - You had some questions about testing
@lenary  - You had some formatting questions 
@topperc  - You had some input just wanted to get your feedback I reduce the coverage quite a bit to have enough testing for this Optimization 

Ref: https://github.com/llvm/llvm-project/pull/124678

https://github.com/llvm/llvm-project/pull/125795