[X86][Btver2] Add support for multiple pipelines stages for x86 scalar schedules. NFCI.

This allows us to use JWriteResIntPair for complex schedule classes (like WriteIDiv) as well as single pipe instructions.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@327686 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed