[X86] Fix Skylake ReadAfterLd for PADDrm etc.

Missed in rL343868 as due to their custom InstrRW.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@344600 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed