[RISCV][InsertVSETVLI] vmv.s.x and fvmv.s.f do not depend on LMUL

We already have this rule encoded elsewhere in the file - which is why we don't see any test changes.  I'm adding it here for completionism.

This is not technically NFC since there could be a test case which isn't caught by the specific rules, but is handled by the generic logic.  I don't have such an example.