Further split cpus test

On GreenDragon, CodeGen/X86/cpus-no-x86_64.ll was still timing out even
after breaking up the original test. I further split off the intel and
AMD cpus which hopefully resolves this.

http://green.lab.llvm.org/green/job/clang-stage2-cmake-RgSan/

llvm-svn: 345438