[llvm] [RISCV] Remove vmv.s.x and vmv.x.s lmul pseudo variants (PR #71501)

[Craig Topper via llvm-commits]

topperc wrote:

What would it take to remove the INSERT_SUBREG/EXTRACT_SUBREG from tblgen? Can we avoid creating the nodes with non-LMUL types in the first place?

https://github.com/llvm/llvm-project/pull/71501