[llvm] [RISCV][MC] Remove register substitutions in `RISCVAsmPrinter`. NFC (PR #102728)

[Craig Topper via llvm-commits]

topperc wrote:

> > This isn't NFC if you have 1174 lines of tests changing...
> 
> 
> 
> But I guess they're just the `InstAlias` which means the underlying instruction is basically the same, is it not NFC under this condition?
> 
> 

If it's observable to the user in any way, it's not NFC.

We want to print the aliases because it's more user friendly.

https://github.com/llvm/llvm-project/pull/102728