[RISCV][AsmParser] Pre-commit test on unsupported vset{i}vli instruction omitting LMUL (NFC)

Author: saveasguy

llvm/test/MC/RISCV/rvv/invalid.s

@@ -1,6 +1,12 @@
 # RUN: not llvm-mc -triple=riscv64 --mattr=+v --mattr=+f %s 2>&1 \
 # RUN:        | FileCheck %s --check-prefix=CHECK-ERROR
 
+vsetvli a2, a0, e8, ta, ma
+# CHECK-ERROR: operand must be e[8|16|32|64],m[1|2|4|8|f2|f4|f8],[ta|tu],[ma|mu]
+
+vsetivli a2, 16, e8, ta, ma
+# CHECK-ERROR: operand must be e[8|16|32|64],m[1|2|4|8|f2|f4|f8],[ta|tu],[ma|mu]
+
 vsetivli a2, 32, e8,m1
 # CHECK-ERROR: operand must be e[8|16|32|64],m[1|2|4|8|f2|f4|f8],[ta|tu],[ma|mu]