[X86][Btver2] Add zero-idiom tests for PSUBS/PSUBUS instructions

Noticed during llvm-exegesis tests, the PSUBS/PSUBUS instructions have the same zero-idiom behaviour to PSUB

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@343319 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed