[llvm] [RISCV] Remove -mattr=+no-rvc-hints (PR #145138)

[Sam Elliott via llvm-commits]

https://github.com/lenary approved this pull request.

I'm happy for this to land, but please wait for a little more consensus than that.

Looking at https://reviews.llvm.org/D62592 (where this landed), @asb said 
> We may later review whether the ability to enable/disable these hints is worth it or not (I know I'd been in favour from the start, but looking at it with fresh eyes I'm not sure it's fully necessary).

Apparently later means 6 years later.


https://github.com/llvm/llvm-project/pull/145138