[llvm] [RISCV][AsmParser] Allow parsing vset{i}vli omitting LMUL parameter (PR #115277)

[Aleksei Romanov via llvm-commits]

saveasguy wrote:

> The godbolt link in the description gives an error rather than demonstrating anything `<source>:3: Error: unrecognized opcode `vsetvli a2,a0,e8,ta,ma', extension `v' or `zve64x' or `zve32x' required`

Sorry, fixed it. Anyway, do we want to proceed with this patch?

https://github.com/llvm/llvm-project/pull/115277