[llvm] [RISCV] Add a tune feature to disable stripping W suffix (PR #86255)

[Wang Pengcheng via llvm-commits]

wangpc-pp wrote:

> > For some implementations, instructions with W suffix would be less
> > costly as they only perform on 32 bits data. Though we may lose some
> > chances to compress.
> 
> Do you know of a real implementation where this true?

Yes, this requirement is from hardware team actually and I didn't notice this stripping W suffix pass before.

https://github.com/llvm/llvm-project/pull/86255